OS/2 Shareware BBS: 10 Tools/10-Tools.zip/S2R10_C.ZIP/S2R10C06.SI

Text File | 1990-03-09 | 66KB | 1,426 lines

.RR--!--!--!--!--!--!--!--!--!--!--!--!--!--!--!--!--!--!--!--!--!--!--!--!--!--!
.PL 62
.LM 1
.RM 78
.MT3
.MB4
.HM1
.FM1
.PO10
.CW10
.SR2
.UJ0
.OJ0
.UL1
.heSCSI Commands and Status                                                3/9/90
.foSCSI-2 draft proposed American National Standard        6-#      Revision 10c
.pn 1
.cp 30
.aw off
.pm 0
6. SCSI Commands and Status
.aw on
.pm 3

ááThi≤ sectioε define≤ thσ SCS╔ commanΣ anΣ statu≤ structure≤ anΣ give≤ ì
severa∞ examples.

ááB∙ keepinτ t∩ ß minimuφ thσ function≤ essentia∞ t∩ communicatσ viß thi≤ ì
protocol¼ ß widσ rangσ oµ periphera∞ device≤ oµ varyinτ capabilit∙ caε operatσ ì
iε thσ samσ environment«  Becausσ subset≤ oµ thσ ful∞ architecturσ ma∙ bσ ì
implemented¼ optiona∞ function≤ arσ noted.

.cp 20
.aw off
.pm 0
6.1. CommanΣ Implementatioε Requirements
.aw on
.pm 3

ááThσ firs⌠ bytσ oµ al∞ SCS╔ command≤ shal∞ contaiε aε operatioε codσ a≤ ì
defineΣ iε thi≤ standard«  Target≤ shal∞ implemen⌠ al∞ command≤ witΦ ß ì
mandator∙ operatioε codσ (seσ 6.1.2⌐ botΦ iε sectioε ╖ anΣ iε thσ appropriatσ ì
sectioε fo≥ thei≥ devicσ type.

.cp 10
.aw off
.pm 0
6.1.1. Reserved
.aw on
.pm 3

ááReserveΣ bits¼ fields¼ bytes¼ anΣ codσ value≤ arσ se⌠ asidσ fo≥ futurσ ì
standardization«  Thei≥ usσ anΣ interpretatioε ma∙ bσ specifieΣ b∙ futurσ ì
extension≤ t∩ thi≤ standard«  ┴ reserveΣ bit¼ field¼ o≥ bytσ shal∞ bσ se⌠ t∩ ì
zero¼ o≥ iε accordancσ witΦ ß futurσ extensioε t∩ thi≤ standard«  ┴ targe⌠ ì
tha⌠ receive≤ ß reserveΣ bit¼ field¼ o≥ bytσ tha⌠ i≤ no⌠ zer∩ o≥ receive≤ ß ì
reserveΣ codσ valuσ shal∞ terminatσ thσ commanΣ witΦ CHEC╦ CONDITIO╬ statu≤ ì
anΣ thσ sensσ ke∙ shal∞ bσ se⌠ t∩ ILLEGA╠ REQUEST«  I⌠ shal∞ als∩ bσ ì
acceptablσ fo≥ ß targe⌠ t∩ interpre⌠ ß bit¼ field¼ byte¼ o≥ codσ valuσ iε ì
accordancσ witΦ ß futurσ extensioε t∩ thi≤ standard.

.cp 20
.aw off
.pm 1
6.1.2. Operatioε Codσ Types
.aw on
.pm 3

.pm 1
Operatioε
Codσ Typσ  Description
¡¡¡¡¡¡¡¡¡  ¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡-
.lm  12
M          Mandator∙ ¡ Command≤ s∩ designateΣ shal∞ bσ implementeΣ iε orde≥ t∩ ì
ááááááááááámee⌠ thσ minimuφ requiremen⌠ oµ thi≤ standard.

O          Optiona∞ ¡ Command≤ s∩ designated¼ iµ implemented¼ shal∞ bσ ì
áááááááááááimplementeΣ a≤ defineΣ iε thi≤ standard.

V          Vendo≥ specifiπ ¡ Operatioε code≤ s∩ designateΣ arσ availablσ fo≥ ì
ááááááááááávendo≥ defineΣ commands«  Seσ thσ vendo≥ specification≤ wherσ ì
ááááááááááácompatibilit∙ i≤ desired.

R          ReserveΣ ¡ Operatioε code≤ s∩ designateΣ shal∞ no⌠ bσ used«  The∙ ì
áááááááááááarσ reserveΣ fo≥ futurσ extension≤ t∩ thi≤ standard.
.lm 1



.cp 14è.aw off
.pm 0
6.2. CommanΣ Descripto≥ Block
.aw on
.pm 3

áá┴ commanΣ i≤ communicateΣ b∙ sendinτ ß commanΣ descripto≥ blocδ t∩ thσ ì
target«  Fo≥ severa∞ commands¼ thσ commanΣ descripto≥ blocδ i≤ accompanieΣ b∙ ì
ß lis⌠ oµ parameter≤ sen⌠ durinτ thσ DAT┴ OU╘ phase«  Seσ thσ specifiπ ì
command≤ fo≥ detaileΣ information.

ááThσ commanΣ descripto≥ blocδ alway≤ ha≤ aε operatioε codσ a≤ it≤ firs⌠ bytσ ì
anΣ ß contro∞ bytσ a≤ it≤ las⌠ byte.

ááFo≥ al∞ commands¼ iµ therσ i≤ aε invaliΣ paramete≥ iε thσ commanΣ descripto≥ ì
block¼ theε thσ targe⌠ shal∞ terminatσ thσ commanΣ withou⌠ alterinτ thσ ì
medium.


.cp 20
.aw off
.pm 1
      Table 6-1: Typical Command Descriptor Block for Six-byte Commands

==============================================================================
  Bit|   7    |   6    |   5    |   4    |   3    |   2    |   1    |   0    |
Byte |        |        |        |        |        |        |        |        |
==============================================================================
 0   |                           Operation Code                              |
-----|-----------------------------------------------------------------------|
 1   |   Logical Unit Number    ⁿ (MSB⌐                                      |
-----|-----------------------------¡                                      ---|
 2   |                           Logical Block Address (if required)         |
-----|--¡                                                                 ---|
 3   |                                                                 (LSB⌐ |
-----|-----------------------------------------------------------------------|
     |                           Transfer Length (if required)               |
 4   ⁿ                           Paramete≥ Lis⌠ LengtΦ (iµ required⌐         |
     |                           Allocatioε LengtΦ (if required)             |
-----|-----------------------------------------------------------------------|
 5   |                           Control                                     |
==============================================================================
.aw on
.pm 3


.cp 26è.aw off
.pm 1
      Table 6-2: Typical Command Descriptor Block for Ten-byte Commands

==============================================================================
  Bit|   7    |   6    |   5    |   4    |   3    |   2    |   1    |   0    |
Byte |        |        |        |        |        |        |        |        |
==============================================================================
 0   |                           Operation Code                              |
-----|-----------------------------------------------------------------------|
 1   |   Logical Unit Number    |                  ReservσΣ                  |
-----|-----------------------------------------------------------------------|
 2   | (MSB)                                                                 |
-----|--¡                                                                 ---|
 3   |                                                                       |
-----|--¡                        Logical Block Address (if required)      ---|
 4   |                                                                       |
-----|--¡                                                                 ---|
 5   |                                                                 (LSB) |
-----|-----------------------------------------------------------------------|
 6   |                           Reserved                                    |
-----|-----------------------------------------------------------------------|
 7   ⁿ (MSB)                     Transfer Length (if required)               |
-----|--¡                        Paramete≥ Lis⌠ LengtΦ (iµ required⌐      ---|
 8   |                           Allocatioε LengtΦ (if required)       (LSB) |
-----|-----------------------------------------------------------------------|
 9   |                           Contro∞                                     |
==============================================================================
.aw on
.pm 3

.cp 30è.aw off
.pm 1
    Table 6-3: Typical Command Descriptor Block for Twelve-byte Commands

==============================================================================
  Bit|   7    |   6    |   5    |   4    |   3    |   2    |   1    |   0    |
Byte |        |        |        |        |        |        |        |        |
==============================================================================
 0   |                           Operation Code                              |
-----|-----------------------------------------------------------------------|
 1   |   Logical Unit Number    |                  ReserveΣ                  |
-----|-----------------------------------------------------------------------|
 2   | (MSB)                                                                 |
-----|--¡                                                                 ---|
 3   |                                                                       |
-----|--¡                        Logical Block Address (if required)      ---|
 4   |                                                                       |
-----|--¡                                                                 ---|
 5   |                                                                 (LSB) |
-----|-----------------------------------------------------------------------|
 6   | (MSB⌐                                                                 |
-----|--¡                                                                 ---|
 7   ⁿ                           Transfer Length (if required)               |
-----|--¡                        Paramete≥ Lis⌠ LengtΦ (iµ required⌐      ---|
 8   |                           Allocatioε LengtΦ (if required)             |
-----|--¡                                                                 ---|
 9   |                                                                 (LSB) |
-----|-----------------------------------------------------------------------|
10   |                           ReserveΣ                                    |
-----|-----------------------------------------------------------------------|
11   |                           Control                                     |
==============================================================================
.aw on
.pm 3

.cp 10
.aw off
.pm 0
6.2.1. Operatioε Code
.aw on
.pm 3

ááThσ operatioε codσ (Tablσ ╢-4⌐ oµ thσ commanΣ descripto≥ blocδ ha≤ ß grou≡ ì
codσ fielΣ anΣ ß commanΣ codσ field«  Thσ threσ-bi⌠ grou≡ codσ fielΣ provide≤ ì
fo≥ eigh⌠ group≤ oµ commanΣ codes«  Thσ fivσ-bi⌠ commanΣ codσ fielΣ provide≤ ì
fo≥ thirt∙-tw∩ commanΣ code≤ iε eacΦ group«  Thus¼ ß tota∞ oµ 25╢ possiblσ ì
operatioε code≤ exist«  Operatioε code≤ arσ defineΣ iε thσ subsequen⌠ Section≤ ì
oµ thi≤ document.

.cp 12
ááThσ grou≡ codσ specifie≤ onσ oµ thσ followinτ groups:

ááGrou≡ ░ ¡ si°-bytσ command≤ (seσ Tablσ ╢-1)
ááGrou≡ ▒ ¡ teε-bytσ command≤ (seσ Tablσ ╢-2)
ááGrou≡ ▓ ¡ teε-bytσ command≤ (seσ Tablσ ╢-2)
ááGrou≡ │ ¡ reserved
ááGrou≡ ┤ ¡ reserved
ááGrou≡ ╡ ¡ twelvσ-bytσ command≤ (seσ Tablσ ╢-3)
ááGrou≡ ╢ ¡ vendo≥ specifiπ
ááGrou≡ ╖ ¡ vendo≥ specific

.cp 8è.aw off
.pm 1
                          Table 6-4: Operation Code

==============================================================================
  Bit|   7    |   6    |   5    |   4    |   3    |   2    |   1    |   0    |
==============================================================================
     |        Group Code        |                Command Code                |
==============================================================================
.aw on
.pm 3


.cp 10
.aw off
.lm 1
.pm 0
6.2.2. Logica∞ Uni⌠ Number
.aw on
.pm 3

ááThσ logica∞ uni⌠ numbe≥ i≤ defineΣ iε thσ IDENTIF┘ messagσ (5.6.7)«  Thσ ì
targe⌠ shal∞ ignorσ thσ logica∞ uni⌠ numbe≥ specifieΣ withiε thσ commanΣ ì
descripto≥ blocδ iµ aε IDENTIF┘ messagσ wa≤ received«  I⌠ i≤ recommendeΣ tha⌠ ì
thσ logica∞ uni⌠ numbe≥ iε thσ commanΣ descripto≥ blocδ bσ se⌠ t∩ zero«

.lm 3
ááNOTICE║  Thσ logica∞ uni⌠ numbe≥ fielΣ i≤ includeΣ iε thσ commanΣ descripto≥ ì
ááblocδ fo≥ compatibilit∙ witΦ somσ SCS╔-▒ devices«  Thi≤ fielΣ ma∙ bσ ì
ááreclaimeΣ iε SCS╔-3«  Ne≈ implementation≤ shoulΣ usσ thσ outbounΣ IDENTIF┘ ì
áámessage¼ whicΦ i≤ mandator∙ iε SCS╔-2¼ t∩ establisΦ thσ I_T_╠ nexus.
.lm 1


.cp 10
.aw off
.pm 0
6.2.3. Logica∞ Blocδ Address
.aw on
.pm 3

ááThσ logica∞ blocδ addres≤ oε logica∞ unit≤ o≥ withiε ß partitioε oε devicσ ì
volume≤ shal∞ begiε witΦ blocδ zer∩ anΣ bσ contiguou≤ u≡ t∩ thσ las⌠ logica∞ ì
blocδ oε tha⌠ logica∞ uni⌠ o≥ withiε tha⌠ partition.

áá┴ si°-bytσ commanΣ descripto≥ blocδ contain≤ ß 2▒-bi⌠ logica∞ blocδ address«  ì
Thσ teε-bytσ anΣ thσ twelvσ-bytσ commanΣ descripto≥ block≤ contaiε 3▓-bi⌠ ì
logica∞ blocδ addresses«  Logica∞ blocδ addresse≤ iε additiona∞ paramete≥ datß ì
havσ thei≥ lengtΦ specifieΣ fo≥ eacΦ occurrence«  Seσ thσ specifiπ commanΣ ì
descriptions.

.cp 10
.aw off
.pm 0
6.2.4. Transfe≥ Length
.aw on
.pm 3

ááThσ transfe≥ lengtΦ fielΣ specifie≤ thσ amoun⌠ oµ datß t∩ bσ transferred¼ ì
usuall∙ thσ numbe≥ oµ blocks«  Fo≥ severa∞ command≤ thσ transfe≥ lengtΦ ì
indicate≤ thσ requesteΣ numbe≥ oµ byte≤ t∩ bσ sen⌠ a≤ defineΣ iε thσ commanΣ ì
description«  Fo≥ thesσ command≤ thσ transfe≥ lengtΦ fielΣ ma∙ bσ identifieΣ ì
b∙ ß differen⌠ name«  Seσ thσ followinτ description≤ anΣ thσ individua∞ ì
commanΣ description≤ fo≥ furthe≥ information.

ááCommand≤ tha⌠ usσ onσ bytσ fo≥ thσ transfe≥ lengtΦ allo≈ u≡ t∩ 25╢ block≤ oµ ì
datß t∩ bσ transferreΣ b∙ onσ command«  ┴ transfe≥ lengtΦ valuσ oµ ▒ t∩ 25╡ ì
indicate≤ thσ numbe≥ oµ block≤ tha⌠ shal∞ bσ transferred«  ┴ valuσ oµ zer∩ ì
indicate≤ 25╢ blocks.

ááIε command≤ tha⌠ usσ multiplσ byte≤ fo≥ thσ transfe≥ length¼ ß transfe≥ ì
lengtΦ oµ zer∩ indicate≤ tha⌠ n∩ datß transfe≥ shal∞ takσ place«  ┴ valuσ oµ ì
onσ o≥ greate≥ indicate≤ thσ numbe≥ oµ block≤ tha⌠ shal∞ bσ transferred.

ááRefe≥ t∩ thσ specifiπ commanΣ descriptioε fo≥ furthe≥ information.

.cp 10è.aw off
.pm 0
6.2.5. Paramete≥ Lis⌠ Length
.aw on
.pm 3

ááThσ paramete≥ lis⌠ lengtΦ i≤ useΣ t∩ specif∙ thσ numbe≥ oµ byte≤ sen⌠ durinτ ì
thσ DAT┴ OU╘ phase«  Thi≤ fielΣ i≤ typicall∙ useΣ iε commanΣ descripto≥ block≤ ì
fo≥ parameter≤ tha⌠ arσ sen⌠ t∩ ß targe⌠ (e.g.¼ modσ parameters¼ diagnostiπ ì
parameters¼ loτ parameters¼ etc.)«  ┴ paramete≥ lengtΦ oµ zer∩ indicate≤ tha⌠ ì
n∩ datß shal∞ bσ transferred«  Thi≤ conditioε shal∞ no⌠ bσ considereΣ a≤ aε ì
error«

.cp 10
.aw off
.pm 0
6.2.6. Allocatioε Length
.aw on
.pm 3

ááThσ allocatioε lengtΦ fielΣ specifie≤ thσ maximuφ numbe≥ oµ byte≤ tha⌠ aε ì
initiato≥ ha≤ allocateΣ fo≥ returneΣ data«  Aε allocatioε lengtΦ oµ zer∩ ì
indicate≤ tha⌠ n∩ datß shal∞ bσ transferred«  Thi≤ conditioε shal∞ no⌠ bσ ì
considereΣ a≤ aε error«  Thσ targe⌠ shal∞ terminatσ thσ DAT┴ I╬ phasσ wheε ì
allocatioε lengtΦ byte≤ havσ beeε transferreΣ o≥ wheε al∞ availablσ datß havσ ì
beeε transferreΣ t∩ thσ initiator¼ whicheve≥ i≤ less«

ááThσ allocatioε lengtΦ i≤ useΣ t∩ limi⌠ thσ maximuφ amoun⌠ oµ datß (e.g.¼ ì
sensσ data¼ modσ data¼ loτ data¼ diagnostiπ data¼ etc.⌐ returneΣ t∩ aε ì
initiator.

.cp 45è.cp 10
.aw off
.pm 0
6.2.7. Contro∞ Field
.aw on
.pm 3

ááThσ contro∞ fielΣ i≤ thσ las⌠ bytσ oµ ever∙ commanΣ descripto≥ block«  Thσ ì
contro∞ fielΣ i≤ defineΣ iε Tablσ ╢-5.

.cp 35
.aw off
.pm 1
                           Table 6-5: Control Field

==============================================================================
  Bit|   7    |   6    |   5    |   4    |   3    |   2    |   1    |   0    |
==============================================================================
     | Vendor specific |         ReserveΣ                  |  Flag  |  Link  |
==============================================================================
.aw on
.pm 3


ááThσ flaτ bi⌠ specifie≤ whicΦ messagσ thσ targe⌠ shal∞ returε t∩ thσ ì
initiato≥ iµ thσ linδ bi⌠ i≤ onσ anΣ thσ commanΣ complete≤ withou⌠ error«  ì
Implementatioε oµ thσ flaτ bi⌠ i≤ optional«

ááThσ flaτ bi⌠ shoulΣ bσ se⌠ t∩ zer∩ iµ thσ linδ bi⌠ i≤ zero«  Iµ linδ bi⌠ i≤ ì
zer∩ anΣ thσ flaτ bi⌠ i≤ one¼ thσ targe⌠ shal∞ returε CHEC╦ CONDITIO╬ status«  ì
Thσ sensσ ke∙ shal∞ bσ se⌠ t∩ ILLEGA╠ REQUEST.

ááIµ thσ flaτ bi⌠ i≤ zer∩ anΣ thσ linδ bi⌠ i≤ one¼ anΣ iµ thσ commanΣ ì
complete≤ successfully¼ thσ targe⌠ shal∞ senΣ thσ LINKE─ COMMAN─ COMPLET┼ ì
message«  Iµ thσ flaτ bi⌠ i≤ onσ anΣ thσ linδ bi⌠ i≤ one¼ anΣ iµ thσ commanΣ ì
complete≤ successfully¼ thσ targe⌠ shal∞ senΣ thσ LINKE─ COMMAN─ COMPLET┼ ì
(WIT╚ FLAG⌐ message«

.pm 0
.lm 3
ááIMPLEMENTOR╙ NOTE║  Thσ flaτ bi⌠ i≤ typicall∙ useΣ t∩ causσ aε interrup⌠ iε ì
ááthσ initiato≥ betweeε linkeΣ commands.
.pm 3
.lm 1

ááThσ linδ bi⌠ i≤ useΣ t∩ continuσ thσ I/╧ proces≤ acros≤ multiplσ commands«  ì
Implementatioε oµ thσ linδ bi⌠ i≤ optional«

áá┴ linδ bi⌠ oµ onσ indicate≤ tha⌠ thσ initiato≥ request≤ ß continuatioε oµ ì
thσ I/╧ proces≤ anΣ tha⌠ thσ targe⌠ shoulΣ ente≥ thσ commanΣ phasσ upoε ì
successfu∞ completioε oµ thσ curren⌠ command«

ááIµ thσ linδ bi⌠ i≤ one¼ anΣ iµ thσ commanΣ complete≤ successfully¼ thσ ì
targe⌠ shal∞ returε INTERMEDIAT┼ o≥ INTERMEDIAT┼-CONDITIO╬ ME╘ statu≤ anΣ ì
shal∞ theε senΣ onσ oµ thσ tw∩ message≤ defineΣ b∙ thσ flaτ bit.

ááIµ eithe≥ oµ thσ linδ anΣ flaτ bit≤ arσ se⌠ t∩ one¼ anΣ thσ targe⌠ doe≤ no⌠ ì
implemen⌠ linkeΣ commands¼ i⌠ shal∞ returε CHEC╦ CONDITIO╬ status«  Thσ sensσ ì
ke∙ shal∞ bσ se⌠ t∩ ILLEGA╠ REQUEST.


.cp 20è.aw off
.pm 0
6.3. Status 
.aw on
.pm 3

ááThσ statu≤ bytσ anΣ statu≤ bytσ codσ arσ specifieΣ iε Table≤ ╢-╢ anΣ ╢-7«  ┴ ì
statu≤ bytσ shal∞ bσ sen⌠ froφ thσ targe⌠ t∩ thσ initiato≥ durinτ thσ STATU╙ ì
phasσ a⌠ thσ completioε oµ eacΦ commanΣ unles≤ thσ commanΣ i≤ terminateΣ b∙ ì
onσ oµ thσ followinτ events║
áá(1⌐ aε ABOR╘ message
áá(2⌐ aε ABOR╘ TA╟ message
áá(3⌐ ß BU╙ DEVIC┼ RESE╘ message
áá(4⌐ ß CLEA╥ QUEU┼ message
áá(5⌐ ß harΣ rese⌠ condition
áá(6⌐ aε unexpecteΣ disconnec⌠ (seσ 5.1.1)

ááThσ STATU╙ phasσ normall∙ occur≤ a⌠ thσ enΣ oµ ß commanΣ bu⌠ iε somσ casσ ì
ma∙ occu≥ prio≥ t∩ transferrinτ thσ commanΣ descripto≥ block.

.cp 10
.aw off
.pm 1
                           Table 6-6: Status Byte

==============================================================================
  Bit|   7    |   6    |   5    |   4    |   3    |   2    |   1    |   0    |
==============================================================================
     |     Reserved    |               Status Byte Code             |Reserved|
==============================================================================
.aw on
.pm 3

.cp 30
.aw off
.pm 1
                         Table 6-7: Status Byte Code 

==============================================================================
     Bits of Status Byte
-----------------------------
7   6   5   4   3   2   1   0    Status
------------------------------------------------------------------------------
R   R   0   0   0   0   0   R    GOOD
R   R   0   0   0   0   1   R    CHECK CONDITION
R   R   0   0   0   1   0   R    CONDITION MET
R   R   0   0   1   0   0   R    BUSY
R   R   0   1   0   0   0   R    INTERMEDIATE
R   R   0   1   0   1   0   R    INTERMEDIATE-CONDITION MET
R   R   0   1   1   0   0   R    RESERVATION CONFLICT
R   R   1   0   0   0   1   R    COMMAN─ TERMINATED
R   R   1   0   1   0   0   R    QUEU┼ FULL

     Al∞ Othe≥ Codes             Reserved
==============================================================================

Key: R - Reserved bit
.aw on
.pm 3

.cp 5
áá┴ definitioε oµ thσ statu≤ bytσ code≤ i≤ giveε below.

ááGOOD.é  Thi≤ statu≤ indicate≤ tha⌠ thσ targe⌠ ha≤ successfull∙ completeΣ thσ ì
command.

ááCHEC╦ CONDITION.é  Thi≤ statu≤ indicate≤ tha⌠ ß contingen⌠ allegiancσ ì
conditioε ha≤ occurreΣ (seσ 6.6).

.c≡ 6èááCONDITIO╬ MET.é  Thi≤ statu≤ o≥ INTERMEDIAT┼-CONDITIO╬ ME╘ i≤ returneΣ ì
wheneve≥ thσ requesteΣ operatioε i≤ satisfieΣ (seσ thσ SEARC╚ DAT┴ anΣ PR┼-ì
FETC╚ commands)«

ááBUSY.é  Thi≤ statu≤ indicate≤ tha⌠ thσ targe⌠ i≤ busy«  Thi≤ statu≤ shal∞ bσ ì
returneΣ wheneve≥ ß targe⌠ i≤ unablσ t∩ accep⌠ ß commanΣ froφ aε otherwisσ ì
acceptablσ initiato≥ (i.e.¼ n∩ reservatioε conflicts)«  Thσ recommendeΣ ì
initiato≥ recover∙ actioε i≤ t∩ issuσ thσ commanΣ agaiε a⌠ ß late≥ time.

.cp 5
ááINTERMEDIATE.é  Thi≤ statu≤ o≥ INTERMEDIAT┼-CONDITIO╬ ME╘ shal∞ bσ returneΣ ì
fo≥ ever∙ successfull∙ completeΣ commanΣ iε ß serie≤ oµ linkeΣ command≤ ì
(excep⌠ thσ las⌠ command)¼ unles≤ thσ commanΣ i≤ terminateΣ witΦ CHEC╦ ì
CONDITION¼ RESERVATIO╬ CONFLICT¼ o≥ COMMAN─ TERMINATE─ status«  Iµ ì
INTERMEDIAT┼ o≥ INTERMEDIAT┼-CONDITIO╬ ME╘ statu≤ i≤ no⌠ returned¼ thσ serie≤ ì
oµ linkeΣ command≤ i≤ terminateΣ anΣ thσ I/╧ proces≤ i≤ ended.

ááINTERMEDIAT┼-CONDITIO╬ MET.é  Thi≤ statu≤ i≤ thσ combinatioε oµ thσ CONDITIO╬ ì
ME╘ anΣ INTERMEDIAT┼ statuses.

ááRESERVATIO╬ CONFLICT.é  Thi≤ statu≤ shal∞ bσ returneΣ wheneve≥ aε initiato≥ ì
attempt≤ t∩ acces≤ ß logica∞ uni⌠ o≥ aε exten⌠ withiε ß logica∞ uni⌠ tha⌠ i≤ ì
reserveΣ witΦ ß conflictinτ reservatioε typσ fo≥ anothe≥ SCS╔ devicσ (seσ thσ ì
RESERV┼ anΣ RESERV┼ UNI╘ commands)«  Thσ recommendeΣ initiato≥ recover∙ actioε ì
i≤ t∩ issuσ thσ commanΣ agaiε a⌠ ß late≥ time.

ááCOMMAN─ TERMINATED.é  Thi≤ statu≤ shal∞ bσ returneΣ wheneve≥ thσ targe⌠ ì
terminate≤ thσ curren⌠ I/╧ proces≤ afte≥ receivinτ ß TERMINAT┼ I/╧ PROCES╙ ì
messagσ (seσ 5.6.22)«  Thi≤ statu≤ als∩ indicate≤ tha⌠ ß contingen⌠ allegiancσ ì
conditioε ha≤ occurreΣ (seσ 6.6).

ááQUEU┼ FULL.é  Thi≤ statu≤ shal∞ bσ implementeΣ iµ taggeΣ queuinτ i≤ ì
implemented«  Thi≤ statu≤ i≤ returneΣ wheε ß SIMPL┼ QUEU┼ TAG¼ ORDERE─ QUEU┼ ì
TAG¼ o≥ HEA─ O╞ QUEU┼ TA╟ messagσ i≤ receiveΣ anΣ thσ commanΣ queuσ i≤ full«  ì
Thσ I/╧ proces≤ i≤ no⌠ placeΣ iε thσ commanΣ queue.
.lm 1
.pm 3

.cp 20
.aw off
.pm 0
6.4. CommanΣ Examples
.aw on
.pm 3

ááThσ followinτ section≤ givσ example≤ oµ typica∞ commanΣ processinτ iε thσ ì
SCS╔ environment«


.cp 10
.aw off
.pm 0
6.4.1. Singlσ CommanΣ Example
.aw on
.pm 3
ááAε I/╧ proces≤ containinτ onσ untaggeΣ REA─ commanΣ i≤ useΣ iε thi≤ sectioε ì
t∩ illustratσ ß simplσ I/╧ proces≤ oε thσ SCS╔ bus«  Thi≤ examplσ doe≤ no⌠ ì
includσ erro≥ o≥ exceptioε conditions.

ááThσ initiato≥ ha≤ onσ se⌠ oµ activσ pointer≤ tha⌠ include≤ ß commanΣ ì
pointer¼ ß datß pointer¼ anΣ ß statu≤ pointer«  Iε addition¼ thσ initiato≥ ha≤ ì
onσ se⌠ oµ saveΣ pointer≤ fo≥ eacΦ I/╧ proces≤ tha⌠ i⌠ i≤ ablσ t∩ concurrentl∙ ì
manage«  Thσ initiato≥ set≤ u≡ thσ saveΣ pointer≤ t∩ poin⌠ t∩ thσ appropriatσ ì
byte≤ fo≥ thσ I/╧ proces≤ anΣ copie≤ thσ saveΣ pointer≤ t∩ thσ activσ ì
pointers«  I⌠ theε arbitrate≤ fo≥ thσ SCS╔ bus¼ anΣ upoε winninτ arbitration¼ ì
select≤ thσ target«  Oncσ thσ targe⌠ i≤ selected¼ thσ targe⌠ assume≤ contro∞ ì
oµ thσ I/╧ process.
è.cp 6
ááDurinτ thσ SELECTIO╬ phase¼ thσ initiato≥ assert≤ thσ AT╬ signa∞ t∩ inforφ ì
thσ targe⌠ tha⌠ thσ initiato≥ wishe≤ t∩ senΣ ß message«  Thσ targe⌠ enter≤ thσ ì
MESSAG┼ OU╘ phasσ anΣ transfer≤ thσ IDENTIF┘ messagσ froφ thσ initiator«  Thi≤ ì
messagσ inform≤ thσ targe⌠ oµ whicΦ logica∞ uni⌠ i≤ t∩ bσ used«  A⌠ thi≤ ì
point¼ aε I_T_╠ nexu≤ ha≤ beeε establisheΣ fo≥ thσ I/╧ process«  Thi≤ nexu≤ ì
associate≤ thσ initiator'≤ pointer≤ witΦ thσ I/╧ process.

ááThσ targe⌠ switche≤ t∩ thσ COMMAN─ phasσ anΣ transfer≤ thσ commanΣ ì
descripto≥ blocδ froφ thσ initiator«  Iε thi≤ case¼ thσ commanΣ descripto≥ ì
blocδ contain≤ ß REA─ command«  Thσ targe⌠ interpret≤ thσ commanΣ anΣ switche≤ ì
t∩ thσ DAT┴ I╬ phase¼ transfer≤ thσ data¼ switche≤ t∩ STATU╙ phase¼ send≤ GOO─ ì
status¼ switche≤ t∩ MESSAG┼ I╬ phase¼ anΣ transfer≤ ß COMMAN─ COMPLET┼ ì
message«  Afte≥ successfull∙ sendinτ thσ COMMAN─ COMPLET┼ message¼ thσ targe⌠ ì
goe≤ t∩ thσ BU╙ FRE┼ phasσ b∙ releasinτ thσ BS┘ signa∞ anΣ thσ I/╧ proces≤ ì
ends.

.cp 10
.aw off
.pm 0
6.4.2. Disconnec⌠ Example
.aw on
.pm 3

ááIε thσ abovσ singlσ commanΣ example¼ thσ lengtΦ oµ timσ necessar∙ t∩ obtaiε ì
thσ datß ma∙ requirσ ß timσ-consuminτ physica∞ positioninτ operation«  Iε ì
orde≥ t∩ improvσ systeφ throughput¼ thσ targe⌠ ma∙ disconnec⌠ froφ thσ ì
initiator¼ thereb∙ freeinτ thσ SCS╔ bu≤ t∩ allo≈ othe≥ I/╧ proces≤ t∩ occur«

ááAfte≥ thσ targe⌠ ha≤ receiveΣ thσ REA─ commanΣ (anΣ ha≤ determineΣ tha⌠ ì
therσ wil∞ bσ ß delay)¼ i⌠ disconnect≤ froφ thσ SCS╔ bu≤ b∙ sendinτ ß ì
DISCONNEC╘ messagσ anΣ b∙ goinτ t∩ thσ BU╙ FRE┼ phase.

ááAfte≥ thσ targe⌠ retrieve≤ thσ requesteΣ datß froφ thσ periphera∞ devicσ i⌠ ì
arbitrate≤ fo≥ thσ SCS╔ bus«  Upoε winninτ arbitration¼ i⌠ reselect≤ thσ ì
initiato≥ anΣ send≤ aε IDENTIF┘ messagσ t∩ thσ initiato≥ viß thσ MESSAG┼ I╬ ì
phase«  Thi≤ revive≤ thσ I_T_╠ nexu≤ s∩ tha⌠ thσ initiato≥ caε retrievσ thσ ì
correc⌠ se⌠ oµ pointer≤ fo≥ thσ I/╧ process«  Thσ initiato≥ restore≤ thσ ì
activσ pointer≤ t∩ thei≥ mos⌠ recen⌠ saveΣ value≤ (which¼ iε thi≤ case¼ arσ ì
thσ initia∞ values⌐ anΣ thσ targe⌠ continue≤ (a≤ iε thσ singlσ commanΣ ì
example⌐ t∩ finisΦ thσ I/╧ process.

ááIµ targe⌠ wishe≤ t∩ disconnec⌠ afte≥ transferrinτ par⌠ oµ thσ datß (e.g.¼ ì
whilσ crossinτ ß cylinde≥ boundary)¼ i⌠ ma∙ d∩ s∩ b∙ sendinτ ß SAV┼ DAT┴ ì
POINTE╥ messagσ anΣ ß DISCONNEC╘ messagσ t∩ thσ initiato≥ anΣ theε ì
disconnecting«  Wheε reconnectioε i≤ completed¼ thσ curren⌠ datß pointe≥ i≤ ì
restoreΣ t∩ it≤ valuσ immediatel∙ prio≥ t∩ thσ SAV┼ DAT┴ POINTE╥ message.

ááOε thosσ occasion≤ wheε aε erro≥ o≥ exceptioε conditioε occur≤ anΣ thσ ì
targe⌠ elect≤ t∩ repea⌠ thσ informatioε transfer¼ thσ targe⌠ ma∙ repea⌠ thσ ì
transfe≥ b∙ eithe≥ issuinτ ß RESTOR┼ POINTER╙ messagσ o≥ b∙ disconnectinτ ì
withou⌠ issuinτ ß SAV┼ DAT┴ POINTE╥ message«  Wheε reconnectioε i≤ completed¼ ì
thσ mos⌠ recen⌠ saveΣ pointe≥ value≤ arσ restored.

.cp 10è.aw off
.pm 0
6.4.3. LinkeΣ CommanΣ Example
.aw on
.pm 3

ááAε I/╧ proces≤ ma∙ contaiε multiplσ command≤ "linkedó together«  Upoε ì
completinτ ß linkeΣ commanΣ successfully¼ thσ targe⌠ automaticall∙ proceed≤ t∩ ì
thσ nex⌠ linkeΣ commanΣ fo≥ thσ I/╧ process«  Al∞ command≤ iε ß serie≤ oµ ì
linkeΣ command≤ arσ addresseΣ t∩ thσ samσ nexu≤ anΣ arσ par⌠ oµ ß singlσ I/╧ ì
process.

ááThσ command≤ arσ no⌠ entirel∙ independent«  Wheε usinτ thσ relativσ addres≤ ì
bi⌠ (seσ 8.1.10)¼ thσ addres≤ oµ thσ las⌠ logica∞ blocδ accesseΣ b∙ onσ oµ thσ ì
command≤ i≤ availablσ t∩ thσ nex⌠ command«  Thu≤ onσ caε searcΦ fo≥ ß ì
particula≥ datß patterε usinτ ß SEARC╚ DAT┴ commanΣ anΣ theε reaΣ thσ logica∞ ì
blocδ containinτ thσ datß patterε witΦ ß REA─ commanΣ linkeΣ t∩ thσ SEARC╚ ì
DAT┴ command«  Onσ caε als∩ reaΣ ß logica∞ blocδ a⌠ ß specifieΣ displacemen⌠ ì
froφ thσ blocδ containinτ thσ datß pattern.

áá┴ LINKE─ COMMAN─ COMPLET┼ o≥ LINKE─ COMMAN─ COMPLET┼ (WIT╚ FLAG⌐ messagσ i≤ ì
sen⌠ froφ thσ targe⌠ t∩ thσ initiato≥ t∩ indicatσ tha⌠ ß linkeΣ commanΣ ì
completed«  Thσ initiato≥ theε update≤ thσ saveΣ pointer≤ fo≥ thσ nexu≤ s∩ ì
tha⌠ subsequen⌠ transfer≤ froφ thσ targe⌠ referencσ thσ nex⌠ commanΣ oµ thσ ì
series«  CommanΣ processinτ oµ linkeΣ anΣ singlσ command≤ i≤ simila≥ excep⌠ ì
tha⌠ relativσ addressinτ i≤ permitteΣ iε linkeΣ commands.

.cp 5
ááFo≥ example¼ ß successfu∞ completioε oµ ß SEARC╚ DAT┴ EQUA╠ commanΣ cause≤ ì
thσ targe⌠ t∩ continuσ witΦ thσ linkeΣ REA─ commanΣ froφ thσ initiator«  Iµ ì
thσ relativσ addres≤ bi⌠ iε thσ REA─ commanΣ ha≤ beeε se⌠ t∩ one¼ anΣ thσ ì
addres≤ fielΣ oµ thσ REA─ commanΣ i≤ se⌠ t∩ zero¼ thσ targe⌠ transfer≤ thσ ì
successfull∙ searcheΣ blocδ t∩ thσ initiator«

.cp 20
.aw off
.pm 0
6.5. CommanΣ Processinτ Consideration≤ anΣ Exceptioε Condition≤ 
.aw on
.pm 3

ááThσ followinτ section≤ describσ somσ exceptioε condition≤ anΣ error≤ ì
associateΣ witΦ commanΣ processinτ anΣ thσ sequencinτ oµ commands.

.cp 10
.aw off
.pm 0
6.5.1. Programmablσ Operatinτ Definition
.aw on
.pm 3

ááSomσ application≤ requirσ tha⌠ thσ operatinτ definitioε oµ ß logica∞ uni⌠ bσ ì
modifieΣ t∩ mee⌠ thσ specia∞ requirement≤ oµ ß particula≥ initiator«  Thσ ì
prograφ-controlleΣ modificatioε oµ thσ operatinτ definitioε i≤ typicall∙ ì
provideΣ t∩ allo≈ operatinτ system≤ t∩ changσ thσ operatinτ definitioε oµ ß ì
morσ recentl∙ developeΣ target≤ t∩ onσ whicΦ i≤ morσ compatiblσ witΦ thσ ì
operatinτ system«  Thi≤ abilit∙ require≤ tha⌠ thσ systeφ compl∙ witΦ thσ lo≈-ì
leve∞ hardwarσ definition≤ oµ SCS╔-2.

ááThσ parameter≤ tha⌠ caε bσ changeΣ b∙ modifyinτ thσ operatinτ definitioε oµ ì
ß logica∞ uni⌠ includσ thσ vendo≥ identification¼ thσ devicσ type¼ thσ devicσ ì
model¼ thσ SCS╔ compliancσ level¼ thσ SCS╔ specificatioε level¼ thσ commanΣ ì
set¼ anΣ othe≥ parameters«  Thσ lo≈-leve∞ hardwarσ parameter≤ includinτ signa∞ ì
timinτ anΣ parit∙ definition≤ canno⌠ bσ changeΣ b∙ modifyinτ thσ operatinτ ì
definition«  Thσ presen⌠ operatinτ definitioε oµ ß logica∞ uni⌠ witΦ respec⌠ ì
t∩ aε initiato≥ caε bσ determineΣ a⌠ an∙ timσ b∙ executioε oµ aε INQUIR┘ ì
command«  Iε somσ vendo≥-specifiπ cases¼ i⌠ ma∙ als∩ bσ necessar∙ t∩ perforφ ì
othe≥ command≤ includinτ MOD┼ SENS┼ anΣ REA─ CAPACITY.

.cp 3èááEacΦ logica∞ uni⌠ begin≤ a⌠ ß particula≥ operatinτ definition«  Iµ thσ ì
logica∞ uni⌠ support≤ thσ CHANG┼ DEFINITIO╬ command¼ thσ presen⌠ operatinτ ì
definitioε caε bσ changeΣ t∩ an∙ othe≥ operatinτ definitioε supporteΣ b∙ thσ ì
logica∞ unit«  Thσ actua∞ detail≤ oµ thσ operatinτ definitioε oµ ß logica∞ ì
uni⌠ arσ vendo≥-specific«  Iµ thσ operatinτ definitioε i≤ changeΣ t∩ onσ tha⌠ ì
doe≤ no⌠ includσ thσ CHANG┼ DEFINITIO╬ command¼ thσ targe⌠ shoulΣ continuσ t∩ ì
accep⌠ thσ CHANG┼ DEFINITIO╬ command.

ááIµ aε erro≥ occur≤ durinτ executioε oµ ß CHANG┼ DEFINITIO╬ command¼ thσ ì
origina∞ operatinτ definitioε remain≤ iε effec⌠ afte≥ thσ commanΣ i≤ executed« ì
Thσ ne≈ operatinτ definitioε become≤ activσ onl∙ afte≥ successfu∞ executioε oµ ì
thσ CHANG┼ DEFINITIO╬ command«

ááSincσ ne≈ operatinτ definition≤ ma∙ precludσ thσ executioε oµ I/╧ processe≤ ì
tha⌠ arσ alread∙ iε progress¼ thσ targe⌠ ma∙ disconnec⌠ t∩ allo≈ completioε oµ ì
an∙ I/╧ processe≤ tha⌠ arσ iε progress«  Operatinτ definitioε change≤ tha⌠ ma∙ ì
causσ conflict≤ witΦ thσ norma∞ operatioε froφ othe≥ initiator≤ shal∞ bσ ì
indicateΣ t∩ thosσ initiator≤ b∙ generatinτ ß uni⌠ attentioε conditioε fo≥ ì
eacΦ othe≥ initiator«  Thσ additiona∞ sensσ codσ shal∞ bσ se⌠ t∩ CHANGE─ ì
OPERATIN╟ DEFINITION.

.cp 10
ááAε initiato≥ ma∙ reques⌠ ß lis⌠ oµ thσ operatinτ definition≤ tha⌠ thσ targe⌠ ì
support≤ anΣ descriptivσ tex⌠ fo≥ eacΦ operatinτ definitioε usinτ thσ INQUIR┘ ì
command.

.cp 10
.aw off
.pm 0
6.5.2. Incorrec⌠ Initiato≥ Connection
.aw on
.pm 3

ááAε incorrec⌠ initiato≥ connectioε occur≤ oε ß reconnectioε if:
áá(1⌐ aε initiato≥ attempt≤ t∩ reconnec⌠ t∩ aε I/╧ process¼ and
áá(2⌐ ß sof⌠ rese⌠ conditioε ha≤ no⌠ occurred¼ anΣ
áá(3⌐ thσ initiato≥ doe≤ no⌠ senΣ aε ABORT¼ ABOR╘ TAG¼ BU╙ DEVIC┼ RESET¼ CLEA╥ ì
QUEUE¼ o≥ TERMINAT┼ I/╧ PROCES╙ messagσ durinτ thσ samσ MESSAG┼ OU╘ phasσ a≤ ì
thσ IDENTIF┘ message.

ááAε incorrec⌠ initiato≥ connectioε als∩ occur≤ oε aε initia∞ connectioε wheε ì
aε initiator:
áá(1⌐ attempt≤ t∩ establisΦ aε I_T_L_╤ nexu≤ wheε aε I_T_╠ nexu≤ alread∙ ì
exist≤ froφ ß previou≤ connection¼ or
áá(2⌐ attempt≤ t∩ establisΦ aε I_T_╠ nexu≤ wheε aε I_T_L_╤ nexu≤ alread∙ ì
exist≤ unles≤ therσ i≤ ß contingen⌠ allegiancσ o≥ extendeΣ contingen⌠ ì
allegiancσ conditioε presen⌠ fo≥ thσ logica∞ uni⌠ o≥ targe⌠ routine.

áá┴ targe⌠ tha⌠ detect≤ aε incorrec⌠ initiato≥ connectioε shal∞ abor⌠ al∞ I/╧ ì
processe≤ fo≥ thσ initiato≥ oε thσ logica∞ uni⌠ o≥ targe⌠ routinσ anΣ shal∞ ì
returε CHEC╦ CONDITIO╬ status«  Thσ sensσ ke∙ shal∞ bσ se⌠ t∩ ABORTE─ COMMAN─ ì
anΣ thσ additiona∞ sensσ codσ shal∞ bσ se⌠ t∩ OVERLAPPE─ COMMAND╙ ATTEMPTED.
.pm 3

ááIµ aε initiato≥ reconnect≤ t∩ aε I/╧ proces≤ anΣ ß sof⌠ rese⌠ conditioε ha≤ ì
occurred¼ thσ targe⌠ shal∞ mee⌠ thσ requirement≤ oµ 5.2.2.2.

.lm 3
ááIMPLEMENTOR╙ NOTES║
áá(1⌐ Aε incorrec⌠ initiato≥ connectioε ma∙ bσ indicativσ oµ ß seriou≤ erro≥ ì
ááand¼ iµ no⌠ detected¼ coulΣ resul⌠ iε aε I/╧ proces≤ operatinτ witΦ ß wronτ ì
ááse⌠ oµ pointers«  Thi≤ i≤ considereΣ ß catastrophiπ failurσ oε thσ par⌠ oµ ì
ááthσ initiator«  Therefore¼ vendo≥-specifiπ erro≥ recover∙ procedure≤ ma∙ bσ ìèáárequireΣ t∩ guaranteσ thσ datß integrit∙ oε thσ medium«  Thσ targe⌠ ma∙ ì
ááreturε additiona∞ sensσ datß t∩ aiΣ iε thi≤ erro≥ recover∙ procedurσ (e.g.¼ ì
áásequentia∞-acces≤ device≤ ma∙ returε thσ residuσ oµ block≤ remaininτ t∩ bσ ì
ááwritteε o≥ reaΣ a⌠ thσ timσ thσ seconΣ commanΣ wa≤ received).
áá(2⌐  Somσ target≤ ma∙ no⌠ detec⌠ aε incorrec⌠ initiato≥ connectioε unti∞ ì
ááafte≥ thσ commanΣ descripto≥ blocδ ha≤ beeε received.
.pm 3
.lm 1


.cp 10
.aw off
.pm 0
6.5.3. Selectioε oµ aε InvaliΣ Logica∞ Unit
.aw on
.pm 3

ááThσ target'≤ responsσ t∩ selectioε oµ ß logica∞ uni⌠ whicΦ i≤ no⌠ valiΣ i≤ ì
describeΣ iε thσ followinτ paragraphs.

ááThσ logica∞ uni⌠ ma∙ no⌠ bσ valiΣ because:
áá(1⌐ thσ targe⌠ doe≤ no⌠ suppor⌠ thσ logica∞ uni⌠ (e.g.¼ somσ target≤ suppor⌠ ì
onl∙ onσ periphera∞ device)«  Iε responsσ t∩ aε INQUIR┘ commanΣ thσ targe⌠ ì
shal∞ returε thσ INQUIR┘ datß witΦ thσ periphera∞ qualifie≥ se⌠ t∩ thσ valuσ ì
requireΣ iε Tablσ ╖-16«  Iε responsσ t∩ an∙ othe≥ commanΣ excep⌠ REQUES╘ SENS┼ ì
thσ targe⌠ shal∞ terminatσ thσ commanΣ witΦ CHEC╦ CONDITIO╬ status«  Iε ì
responsσ t∩ ß REQUES╘ SENS┼ commanΣ thσ targe⌠ shal∞ returε sensσ data«  Thσ ì
sensσ ke∙ shal∞ bσ se⌠ t∩ ILLEGA╠ REQUES╘ anΣ thσ additiona∞ sensσ codσ shal∞ ì
bσ se⌠ t∩ LOGICA╠ UNI╘ NO╘ SUPPORTED.
.cp 8
áá(2⌐ thσ targe⌠ support≤ thσ logica∞ unit¼ bu⌠ thσ periphera∞ devicσ i≤ no⌠ ì
currentl∙ attacheΣ t∩ thσ target«  Iε responsσ t∩ aε INQUIR┘ commanΣ thσ ì
targe⌠ shal∞ returε thσ INQUIR┘ datß witΦ thσ periphera∞ qualifie≥ se⌠ t∩ thσ ì
valuσ requireΣ iε Tablσ ╖-16«  Iε responsσ t∩ an∙ othe≥ commanΣ excep⌠ REQUES╘ ì
SENS┼ thσ targe⌠ shal∞ terminatσ thσ commanΣ witΦ CHEC╦ CONDITIO╬ status«  Iε ì
responsσ t∩ ß REQUES╘ SENS┼ commanΣ thσ targe⌠ shal∞ returε sensσ data«  Thσ ì
sensσ ke∙ shal∞ bσ se⌠ t∩ ILLEGA╠ REQUES╘ anΣ thσ additiona∞ sensσ codσ shal∞ ì
bσ se⌠ t∩ LOGICA╠ UNI╘ NO╘ SUPPORTED.
.cp 5
áá(3⌐ thσ targe⌠ support≤ thσ logica∞ uni⌠ anΣ thσ periphera∞ devicσ i≤ ì
attached¼ bu⌠ no⌠ operational«  Iε responsσ t∩ aε INQUIR┘ commanΣ thσ targe⌠ ì
shal∞ returε thσ INQUIR┘ datß witΦ thσ periphera∞ qualifie≥ se⌠ t∩ thσ valuσ ì
requireΣ iε Tablσ ╖-16«  Thσ target'≤ responsσ t∩ an∙ commanΣ othe≥ thaε ì
INQUIR┘ anΣ REQUES╘ SENS┼ i≤ vendo≥ specific.
áá(4⌐ thσ targe⌠ support≤ thσ logica∞ uni⌠ bu⌠ i≤ incapablσ oµ determininτ iµ ì
thσ periphera∞ devicσ i≤ attacheΣ o≥ i≤ no⌠ operationa∞ wheε i⌠ i≤ no⌠ ready«  ì
Iε responsσ t∩ aε INQUIR┘ commanΣ thσ targe⌠ shal∞ returε thσ INQUIR┘ datß ì
witΦ thσ periphera∞ qualifie≥ se⌠ t∩ thσ valuσ requireΣ iε Tablσ ╖-16«  Iε ì
responsσ t∩ ß REQUES╘ SENS┼ commanΣ thσ targe⌠ shal∞ returε thσ REQUES╘ SENS┼ ì
datß witΦ ß sensσ ke∙ oµ N╧ SENS┼ unles≤ ß prio≥ erro≥ conditioε exists«  Thσ ì
target'≤ responsσ t∩ an∙ othe≥ commanΣ i≤ vendo≥ specific.

.cp 10
.aw off
.pm 0
6.5.4. Paramete≥ Rounding
.aw on
.pm 3

ááCertaiε parameter≤ sen⌠ t∩ ß targe⌠ witΦ variou≤ command≤ contaiε ß rangσ oµ ì
values«  Target≤ ma∙ choosσ t∩ implemen⌠ onl∙ selecteΣ value≤ froφ thi≤ range«  ì
Wheε thσ targe⌠ receive≤ ß valuσ tha⌠ i⌠ doe≤ no⌠ support¼ i⌠ eithe≥ reject≤ ì
thσ commanΣ (CHEC╦ CONDITIO╬ statu≤ witΦ ILLEGA╠ REQUES╘ sensσ key⌐ o≥ i⌠ ì
round≤ thσ valuσ receiveΣ t∩ ß supporteΣ value«  Thσ targe⌠ shal∞ rejec⌠ ì
unsupporteΣ value≤ unles≤ roundinτ i≤ permitteΣ iε thσ descriptioε oµ thσ ì
parameter.

ááRoundinτ oµ paramete≥ values¼ wheε permitted¼ shal∞ bσ performeΣ a≤ follows║  ì
┴ targe⌠ tha⌠ receive≤ ß paramete≥ valuσ tha⌠ i≤ no⌠ aε exac⌠ supporteΣ valuσ ìèshal∞ adjus⌠ thσ valuσ t∩ onσ tha⌠ i⌠ support≤ anΣ shal∞ returε CHEC╦ ì
CONDITIO╬ statu≤ witΦ ß sensσ ke∙ oµ RECOVERE─ ERROR«  Thσ additiona∞ sensσ ì
codσ shal∞ bσ se⌠ t∩ ROUNDE─ PARAMETER«  Thσ initiato≥ i≤ responsiblσ t∩ issuσ ì
aε appropriatσ commanΣ t∩ learε wha⌠ valuσ thσ targe⌠ ha≤ selected.

.lm 3
ááIMPLEMENTOR╙ NOTE║  Generally¼ thσ targe⌠ shoulΣ adjus⌠ maximuφ-valuσ field≤ ì
áádowε t∩ thσ nex⌠ lowe≥ supporteΣ valuσ thaε thσ onσ specifieΣ b∙ thσ ì
ááinitiator«  Minimuφ-valuσ field≤ shoulΣ bσ roundeΣ u≡ t∩ thσ nex⌠ highe≥ ì
áásupporteΣ valuσ thaε thσ onσ specifieΣ b∙ thσ initiator«  Iε somσ cases¼ thσ ì
áátypσ oµ roundinτ (u≡ o≥ down⌐ i≤ explicitl∙ specifieΣ iε thσ descriptioε oµ ì
ááthσ parameter.
.lm 1

.cp 20
.aw off
.pm 0
6.5.5. Asynchronou≤ Even⌠ Notificatioε 
.aw on
.pm 3

ááImplementatioε oµ asynchronou≤ even⌠ notificatioε i≤ optional«  Thi≤ ì
protoco∞ caε bσ useΣ t∩ inforφ processo≥ device≤ tha⌠ aε asynchronou≤ even⌠ ì
ha≤ occurred«  ┴ SEN─ commanΣ witΦ aε AE╬ bi⌠ oµ onσ i≤ issueΣ t∩ ß processo≥ ì
devicσ witΦ ß subsequen⌠ datß phasσ tha⌠ include≤ thσ REQUES╘ SENS┼ ì
information«  SCS╔ device≤ tha⌠ responΣ t∩ aε INQUIR┘ commanΣ a≤ ß processo≥ ì
devicσ typσ witΦ asynchronou≤ even⌠ notificatioε capabilit∙ ma∙ bσ notifieΣ oµ ì
asynchronou≤ event≤ usinτ thi≤ protocol«  Aε SCS╔ devicσ ha≤ t∩ bσ capablσ oµ ì
actinτ a≤ aε initiato≥ iε orde≥ t∩ perforφ asynchronou≤ even⌠ notification.

.lm 3
ááIMPLEMENTOR╙ NOTE║  Asynchronou≤ even⌠ notificatioε canno⌠ bσ useΣ witΦ ß ì
áádevicσ tha⌠ act≤ a≤ ß temporar∙ initiato≥ (e.g.¼ device≤ executinτ COP┘ ì
áácommands⌐ sincσ the∙ arσ no⌠ identifieΣ a≤ ß processo≥ device.
.lm 1

ááParameter≤ affectinτ thσ usσ oµ asynchronou≤ even⌠ notificatioε arσ ì
containeΣ iε thσ contro∞ modσ pagσ (seσ 7.3.3.1).

ááThσ fou≥ use≤ oµ asynchronou≤ even⌠ notificatioε are:
áá(1⌐ informinτ ß processo≥ oµ aε erro≥ conditioε encountereΣ afte≥ commanΣ ì
completion
áá(2⌐ informinτ al∞ processo≥ device≤ tha⌠ ß newl∙ initializeΣ devicσ i≤ ì
available
áá(3⌐ informinτ al∞ processo≥ device≤ oµ othe≥ uni⌠ attentioε conditions
áá(4⌐ informinτ al∞ processo≥ device≤ oµ othe≥ asynchronou≤ events.
.lm1
.pm 3

ááOthe≥ use≤ oµ asynchronou≤ even⌠ notificatioε arσ no⌠ prohibited¼ howeve≥ ì
thi≤ protoco∞ i≤ no⌠ intendeΣ t∩ bσ useΣ whilσ aε I_T_╠ o≥ I_T_L_╤ nexu≤ ì
exist≤ betweeε thσ processo≥ devicσ (i.e.¼ thσ initiato≥ oµ thσ nexus⌐ anΣ thσ ì
othe≥ SCS╔ devicσ (i.e.¼ thσ targe⌠ oµ thσ nexus)«  Asynchronou≤ even⌠ ì
notificatioε i≤ no⌠ intendeΣ fo≥ usσ witΦ targe⌠ routine≤ (i.e.¼ aε I_T_╥ o≥ ì
I_T_R_╤ nexus).

ááAε examplσ oµ thσ firs⌠ casσ abovσ i≤ ß devicσ tha⌠ implement≤ ß writσ ì
cache«  Iµ thσ targe⌠ i≤ unablσ t∩ writσ cacheΣ datß t∩ thσ medium¼ i⌠ ma∙ usσ ì
aε asynchronou≤ even⌠ notificatioε t∩ inforφ thσ initiato≥ oµ thσ failure«  Aε ì
extendeΣ contingen⌠ allegiancσ conditioε ma∙ als∩ bσ establisheΣ durinτ thσ ì
samσ I_T_╠ nexu≤ useΣ fo≥ thσ asynchronou≤ even⌠ notificatioε (seσ 5.6.9).

.cp 5èááAε examplσ oµ thσ thirΣ casσ abovσ i≤ ß devicσ tha⌠ support≤ removablσ ì
media«  Asynchronou≤ even⌠ notificatioε ma∙ bσ useΣ t∩ inforφ aε initiato≥ oµ ì
ß no⌠-read∙-t∩-read∙ transitioε (mediuφ changed⌐ o≥ oµ aε operato≥ initiateΣ ì
even⌠ (e.g.¼ activatinτ ß writσ protec⌠ switcΦ o≥ activatinτ ß star⌠ o≥ sto≡ ì
switch).

.cp 5
ááAε examplσ oµ thσ fourtΦ casσ abovσ i≤ ß sequentia∞-acces≤ devicσ performinτ ì
ß REWIN─ commanΣ witΦ thσ immediatσ bi⌠ se⌠ t∩ one«  Asynchronou≤ even⌠ ì
notificatioε ma∙ bσ useΣ t∩ inforφ aε initiato≥ tha⌠ thσ beginninτ oµ mediuφ ì
ha≤ beeε reached«  Completioε oµ ß C─-RO═ AUDI╧ PLA┘ commanΣ starteΣ iε thσ ì
immediatσ modσ i≤ anothe≥ examplσ oµ thi≤ case.

ááNotificatioε oµ aε asynchronou≤ even⌠ i≤ performeΣ usinτ thσ SEN─ commanΣ ì
witΦ thσ AE╬ bi⌠ se⌠ t∩ one«  Thσ informatioε identifyinτ thσ conditioε beinτ ì
reporteΣ shal∞ bσ returneΣ durinτ thσ DAT┴ OU╘ phasσ oµ thσ SEN─ commanΣ (seσ ì
11.2.2.)«  Thσ datß sen⌠ i≤ showε iε Tablσ 1▒-4.

.cp 5
ááAε erro≥ conditioε o≥ uni⌠ attentioε conditioε shal∞ bσ reporteΣ oncσ pe≥ ì
occurrencσ oµ thσ even⌠ causinτ it«  Thσ targe⌠ ma∙ choosσ t∩ usσ aε ì
asynchronou≤ even⌠ notificatioε o≥ t∩ returε CHEC╦ CONDITIO╬ statu≤ oε ß ì
subsequen⌠ command¼ bu⌠ no⌠ both«  Notificatioε oµ commanΣ-relateΣ erro≥ ì
condition≤ shal∞ bσ sen⌠ onl∙ t∩ thσ processo≥ tha⌠ initiateΣ thσ I/╧ process.

ááThσ asynchronou≤ even⌠ notificatioε protoco∞ caε bσ useΣ t∩ notif∙ processo≥ ì
device≤ tha⌠ ß systeφ resourcσ ha≤ becomσ available«  Iµ ß targe⌠ choose≤ t∩ ì
usσ thi≤ method¼ thσ sensσ ke∙ iε thσ sensσ datß sen⌠ t∩ thσ processo≥ devicσ ì
shal∞ bσ se⌠ t∩ UNI╘ ATTENTION«

ááThσ asynchronou≤ even⌠ notificatioε protoco∞ shal∞ bσ useΣ onl∙ t∩ SCS╔ ì
device≤ tha⌠ returε processo≥ devicσ typσ witΦ aε AEN├ bi⌠ oµ onσ iε responsσ ì
t∩ aε INQUIR┘ command«  Thσ INQUIR┘ commanΣ shoulΣ bσ issueΣ t∩ logica∞ uni⌠ ì
zer∩ oµ eacΦ SCS╔ devicσ respondinτ t∩ selection«  Thi≤ procedurσ shal∞ bσ ì
conducteΣ prio≥ t∩ thσ firs⌠ asynchronou≤ even⌠ notificatioε anΣ shal∞ bσ ì
repeateΣ wheneve≥ thσ devicσ deem≤ i⌠ appropriatσ o≥ wheε aε even⌠ occur≤ tha⌠ ì
ma∙ invalidatσ thσ curren⌠ information«  (Seσ 5.6.21¼ SYNCHRONOU╙ DAT┴ ì
TRANSFE╥ REQUES╘ message¼ fo≥ example≤ oµ thesσ events.)

ááEacΦ SCS╔ devicσ tha⌠ return≤ processo≥ devicσ typσ witΦ aε AEN├ bi⌠ oµ onσ ì
shal∞ bσ issueΣ ß TES╘ UNI╘ READ┘ commanΣ t∩ determinσ tha⌠ thσ SCS╔ devicσ i≤ ì
read∙ t∩ receivσ aε asynchronou≤ even⌠ notification«  Aε SCS╔ devicσ returninτ ì
CHEC╦ CONDITIO╬ statu≤ i≤ issueΣ ß REQUES╘ SENS┼ command«  Thi≤ clear≤ an∙ ì
pendinτ uni⌠ attentioε condition«  Aε SCS╔ devicσ tha⌠ return≤ processo≥ ì
devicσ typσ witΦ aε AEN├ bi⌠ oµ onσ anΣ return≤ GOO─ statu≤ wheε issueΣ ß TES╘ ì
UNI╘ READ┘ commanΣ shal∞ accep⌠ ß SEN─ commanΣ witΦ aε AE╬ bi⌠ oµ one.

.lm 3
ááIMPLEMENTOR╙ NOTE║ Aε SCS╔ devicσ whicΦ caε usσ asynchronou≤ even⌠ ì
áánotificatioε a⌠ initializatioε timσ shoulΣ providσ mean≤ t∩ defea⌠ thesσ ì
áánotifications«  Thi≤ caε bσ donσ witΦ ß switcΦ o≥ jumpe≥ wire«  Device≤ ì
ááwhicΦ implemen⌠ saveΣ parameter≤ ma∙ alternativel∙ savσ thσ asynchronou≤ ì
ááeven⌠ notificatioε permission≤ eithe≥ oε ß pe≥ SCS╔ devicσ basi≤ o≥ a≤ ß ì
áásysteφ widσ option«  Iε an∙ case¼ ß devicσ conduct≤ ß surve∙ witΦ INQUIR┘ ì
áácommand≤ t∩ bσ surσ tha⌠ thσ device≤ oε thσ SCS╔ bu≤ arσ appropriatσ ì
áádestination≤ fo≥ SEN─ command≤ witΦ aε AE╬ bi⌠ oµ one«  (Thσ device≤ oε thσ ì
áábu≤ o≥ thσ SCS╔ I─ assignment≤ ma∙ havσ changed.⌐
.lm 1
è.pm 0
6.5.6. UnexpecteΣ Reselection
.aw on
.pm 3

ááAε unexpecteΣ reselectioε occur≤ iµ ßε SCSI device attempt≤ t∩ reconnec⌠ t∩ ì
aε I/╧ proces≤ fo≥ whicΦ ß nexu≤ doe≤ no⌠ exist«  Aε SCS╔ devicσ shoulΣ ì
responΣ t∩ aε unexpecteΣ reselectioε b∙ sendinτ aε ABOR╘ message.

.cp 20
.aw off
.pm 0
6.6. Contingent Allegiancσ Condition
.aw on
.pm 3

.cp 7
ááThσ contingen⌠ allegiancσ conditioε shal∞ exis⌠ followinτ thσ returε oµ ì
CHEC╦ CONDITIO╬ o≥ COMMAN─ TERMINATE─ statu≤ anΣ ma∙ optionall∙ exis⌠ ì
followinτ aε unexpecteΣ disconnect«  Thσ contingen⌠ allegiancσ conditioε shal∞ ì
bσ preserveΣ fo≥ thσ I_T_° nexu≤ unti∞ i⌠ i≤ cleared«  Thσ contingen⌠ ì
allegiancσ conditioε shal∞ bσ cleareΣ upoε thσ generatioε oµ ß harΣ rese⌠ ì
condition¼ o≥ b∙ aε ABOR╘ message¼ ß BU╙ DEVIC┼ RESE╘ message¼ o≥ an∙ ì
subsequen⌠ commanΣ fo≥ thσ I_T_° nexus«  Whilσ thσ contingen⌠ allegiancσ ì
conditioε exist≤ thσ targe⌠ shal∞ preservσ thσ sensσ datß fo≥ thσ initiator«

ááWhilσ thσ contingen⌠ allegiancσ conditioε exists¼ iµ thσ targe⌠ i≤ unablσ t∩ ì
maintaiε separatσ sensσ data¼ thσ targe⌠ shal∞ responΣ t∩ an∙ othe≥ request≤ ì
fo≥ acces≤ t∩ thσ logica∞ uni⌠ o≥ targe⌠ routinσ froφ anothe≥ initiato≥ witΦ ß ì
BUS┘ status«  Executioε oµ queueΣ command≤ fo≥ thσ logica∞ uni⌠ o≥ targe⌠ ì
routinσ fo≥ whicΦ thσ contingen⌠ allegiancσ conditioε exist≤ shal∞ bσ ì
suspendeΣ unti∞ thσ contingen⌠ allegiancσ conditioε i≤ cleared.

.aw off
.pm 0
6.7. Extended Contingent Allegiance Condition
.aw on
.pm 3

ááImplementatioε oµ extendeΣ contingen⌠ allegiancσ i≤ optional«  Thσ extendeΣ ì
contingen⌠ allegiancσ conditioε extend≤ thσ contingen⌠ allegiancσ conditioε ì
fo≥ aε I_T_° nexus«  Thi≤ conditioε i≤ generateΣ b∙ thσ targe⌠ sendinτ aε ì
INITIAT┼ RECOVER┘ messagσ t∩ thσ initiato≥ followinτ CHEC╦ CONDITIO╬ o≥ ì
COMMAN─ TERMINATE─ statu≤ anΣ prio≥ t∩ thσ COMMAN─ COMPLET┼ message«  Thi≤ ì
conditioε shal∞ bσ preserveΣ unti∞ i⌠ i≤ cleareΣ b∙ ß BU╙ DEVIC┼ RESE╘ ì
message¼ ß RELEAS┼ RECOVER┘ message¼ o≥ ß harΣ rese⌠ condition.

ááWhilσ thσ extendeΣ contingen⌠ allegiancσ conditioε exist≤ thσ targe⌠ shal∞ ì
responΣ t∩ an∙ othe≥ reques⌠ fo≥ acces≤ t∩ thσ logica∞ uni⌠ froφ anothe≥ ì
initiato≥ witΦ BUS┘ status«  Executioε oµ queueΣ command≤ fo≥ thσ logica∞ uni⌠ ì
fo≥ whicΦ thσ extendeΣ contingen⌠ allegiancσ conditioε exist≤ shal∞ bσ ì
suspendeΣ unti∞ thσ RELEAS┼ RECOVER┘ messagσ i≤ receiveΣ b∙ thσ target.

.lm 3
ááIMPLEMENTOR╙ NOTES║
áá(1⌐ I⌠ i≤ no⌠ requireΣ t∩ generatσ aε extendeΣ contingen⌠ allegiancσ ì
ááconditioε fo≥ ever∙ CHEC╦ CONDITIO╬ o≥ COMMAN─ TERMINATE─ statu≤ tha⌠ ì
ááoccurs«  Simplσ error≤ no⌠ requirinτ aε extendeΣ recover∙ ma∙ bσ deal⌠ witΦ ì
ááb∙ usinτ thσ contingen⌠ allegiancσ protocol.
áá(2⌐ Durinτ thσ existencσ oµ thσ extendeΣ contingen⌠ allegiancσ condition¼  ì
ááappropriatσ erro≥ recover∙ sequence≤ ma∙ bσ executed«  SucΦ command≤ caε ì
áácorrec⌠ data¼ modif∙ o≥ deletσ queueΣ commands¼ perforφ LO╟ SENS┼ command≤ ì
ááanΣ obtaiε diagnostiπ information«  ExtendeΣ contingen⌠ allegiancσ i≤ ì
áárecommendeΣ fo≥ erro≥ condition≤ tha⌠ ma∙ requirσ executioε oµ multiplσ-ste≡ ì
ááerro≥-recover∙ protocol≤ withou⌠ interferencσ froφ othe≥ initiators.
.lm 1

.cp 4èááAε extendeΣ contingen⌠ allegiancσ conditioε ma∙ als∩ bσ generateΣ usinτ aε ì
asynchronou≤ even⌠ notificatioε protocol«  Wheε thσ even⌠ i≤ detected¼ thσ bu≤ ì
devicσ whicΦ detecteΣ thσ even⌠ assume≤ thσ initiato≥ rolσ anΣ transmit≤ ß ì
SEN─ commanΣ witΦ aε AE╬ bi⌠ oµ onσ t∩ thσ appropriatσ device(s⌐ (seσ 11.2.2).

.cp 3
ááIµ thσ devicσ wishe≤ t∩ generatσ aε extendeΣ contingen⌠ allegiancσ conditioε ì
durinτ aε asynchronou≤ even⌠ notification¼ i⌠ shal∞ senΣ aε INITIAT┼ RECOVER┘ ì
messagσ followinτ thσ IDENTIF┘ messagσ (anΣ followinτ an∙ queuσ taτ message⌐ ì
anΣ prio≥ t∩ thσ COMMAN─ phasσ oµ thσ SEN─ command«  Aε extendeΣ contingen⌠ ì
allegiancσ conditioε caε bσ generateΣ fo≥ onl∙ onσ I_T_╠ nexu≤ a⌠ ß time«  Thσ ì
extendeΣ contingen⌠ allegiancσ conditioε i≤ cleareΣ wheε ß RELEAS┼ RECOVER┘ ì
messagσ i≤ receiveΣ froφ thσ devicσ t∩ whicΦ thσ INITIAT┼ RECOVER┘ messagσ wa≤ ì
sent«  Thσ generatioε oµ ß harΣ rese⌠ condition¼ o≥ receip⌠ oµ ß BU╙ DEVIC┼ ì
RESE╘ messagσ shal∞ als∩ clea≥ thσ extendeΣ contingen⌠ allegiancσ condition.

ááDurinτ aε extendeΣ contingen⌠ allegiancσ onl∙ untaggeΣ I/╧ processe≤ froφ ì
thσ SCS╔ devicσ t∩ whicΦ thσ INITIAT┼ RECOVER┘ messagσ wa≤ sen⌠ shal∞ bσ ì
executeΣ b∙ thσ target«  Iµ thσ initiato≥ send≤ ß queuσ taτ messagσ thσ targe⌠ ì
shal∞ responΣ witΦ QUEU┼ FUL╠ status«  Afte≥ thσ extendeΣ contingen⌠ ì
allegiancσ conditioε i≤ cleareΣ an∙ command≤ remaininτ iε thσ commanΣ queuσ ì
shal∞ bσ executed.

.cp 20
.aw off
.pm 0
6.8. QueueΣ I/O Processes
.aw on
.pm 3

ááThσ implementatioε oµ queuinτ fo≥ I/╧ processe≤ i≤ optional«  Queuinτ oµ I/╧ ì
processe≤ allow≤ ß targe⌠ t∩ accep⌠ multiplσ I/╧ processe≤ fo≥ executioε a⌠ ß ì
late≥ time«

ááTherσ arσ tw∩ method≤ fo≥ implementatioε oµ queuing¼ taggeΣ anΣ untagged« ì
TaggeΣ queuinτ allow≤ ß targe⌠ t∩ accep⌠ multiplσ I/╧ processe≤ froφ eacΦ ì
initiato≥ fo≥ eacΦ logica∞ uni⌠ o≥ targe⌠ routine«  UntaggeΣ queuinτ allow≤ ß ì
targe⌠ t∩ accep⌠ onσ I/╧ proces≤ froφ eacΦ initiato≥ fo≥ eacΦ logica∞ unit«

áá┴ targe⌠ ma∙ bσ capablσ oµ botΦ method≤ oµ queuing¼ bu⌠ onl∙ onσ methoΣ ma∙ ì
bσ useΣ b∙ aε initiato≥ a⌠ ß time«  Othe≥ initiator≤ ma∙ choosσ thσ othe≥ ì
queuinτ method╗ iε tha⌠ case¼ thσ targe⌠ ma∙ managσ botΦ type≤ oµ queueΣ ì
commands.

ááUntaggeΣ queuinτ ma∙ bσ supporteΣ b∙ SCS╔-▒ o≥ SCS╔-▓ devices«  TaggeΣ ì
queuinτ i≤ ne≈ iε SCS╔-2.

.cp 10
.aw off
.pm 0
6.8.1. UntaggeΣ Queuing
.aw on
.pm 3

.cp3
ááUntaggeΣ queuinτ allow≤ ß targe⌠ t∩ accep⌠ ß commanΣ froφ aε initiato≥ fo≥ ß ì
logica∞ uni⌠ o≥ targe⌠ routinσ whilσ ß commanΣ froφ anothe≥ initiato≥ i≤ beinτ ì
executed«  Onl∙ onσ commanΣ fo≥ eacΦ I_T_° nexu≤ shal∞ bσ accepteΣ a⌠ ß time«

.cp 6
ááAε I/╧ proces≤ ma∙ bσ initiateΣ an∙ timσ thσ BU╙ FRE┼ phasσ exist≤ eveε iµ ì
aε I/╧ proces≤ froφ ß differen⌠ initiato≥ i≤  active«  Iµ thσ disconnec⌠ ì
privilegσ i≤ no⌠ granteΣ iε thσ IDENTIF┘ messagσ oµ thσ ne≈ I/╧ process¼ thσ ì
targe⌠ ma∙ eithe≥ suspenΣ thσ activσ I/╧ proces≤ o≥ i⌠ ma∙ returε BUS┘ statu≤ ì
t∩ thσ ne≈ I/╧ process.

.cp 4èááThσ I_T_° nexu≤ sufficientl∙ specifie≤ thσ relationshi≡ s∩ tha⌠ thσ targe⌠ ì
caε reconnec⌠ t∩ thσ initiato≥ t∩ restorσ thσ pointer≤ fo≥ I/╧ proces≤ a≤ lonτ ì
a≤ onl∙ onσ I/╧ proces≤ pe≥ I_T_° nexu≤ i≤ issued«  I⌠ i≤ thσ responsibilit∙ ì
oµ thσ initiato≥ t∩ assurσ tha⌠ onl∙ onσ sucΦ I/╧ proces≤ i≤ issueΣ a⌠ an∙ ì
timσ (seσ 6.5.2).

.cp 10
.aw off
.pm 0
6.8.2. TaggeΣ Queuing
.aw on
.pm 3

ááTaggeΣ queuinτ allow≤ ß targe⌠ t∩ accep⌠ multiplσ I/╧ processe≤ froφ thσ ì
samσ o≥ differen⌠ initiator≤ unti∞ thσ logica∞ unit'≤ commanΣ queuσ i≤ full«  ì
Iµ aε I/╧ proces≤ i≤ receiveΣ anΣ thσ commanΣ queuσ i≤ full¼ thσ targe⌠ shal∞ ì
terminatσ thσ I/╧ proces≤ witΦ QUEU┼ FUL╠ status«

ááThσ commanΣ queuσ i≤ setu≡ b∙ thσ targe⌠ fo≥ eacΦ supporteΣ logica∞ uni⌠ anΣ ì
targe⌠ routine«  Initiator≤ ma∙ adΣ o≥ deletσ I/╧ processe≤ t∩ thσ queue«  ì
Wheε addinτ aε I/╧ process¼ thσ initiato≥ ma∙ specif∙ fixeΣ orde≥ oµ ì
execution¼ allo≈ thσ targe⌠ t∩ definσ thσ orde≥ oµ execution¼ o≥ specif∙ tha⌠ ì
thσ I/╧ proces≤ i≤ t∩ bσ executeΣ next.

ááIµ thσ disconnec⌠ privilegσ i≤ no⌠ granteΣ iε thσ IDENTIF┘ messagσ fo≥ ß ì
taggeΣ I/╧ proces≤ thσ targe⌠ shal∞ returε BUS┘ status.

ááThσ queuσ taτ message≤ (seσ 5.6.17⌐ allo≈ thσ initiato≥ t∩ establisΦ ß ì
uniquσ I_T_L_╤ nexu≤ t∩ identif∙ eacΦ I/╧ process«  Thσ I_T_L_╤ nexu≤ allow≤ ì
thσ targe⌠ t∩ reconnec⌠ t∩ ß specifiπ I/╧ proces≤ anΣ allow≤ thσ initiato≥ t∩ ì
restorσ thσ se⌠ oµ pointer≤ fo≥ tha⌠ I/╧ process«  Aε initiato≥ ma∙ havσ ì
severa∞ I/╧ processe≤ ongoinτ t∩ thσ samσ o≥ differen⌠ logica∞ unit≤ o≥ targe⌠ ì
routine≤ a≤ lonτ a≤ eacΦ ha≤ ß uniquσ nexus.

.cp 5
ááIµ onl∙ SIMPL┼ QUEU┼ TA╟ message≤ arσ used¼ thσ targe⌠ ma∙ executσ thσ ì
command≤ iε an∙ orde≥ tha⌠ i≤ deemeΣ desirablσ withiε thσ constraint≤ oµ thσ ì
queuσ managemen⌠ algorithφ specifieΣ iε thσ contro∞ modσ pagσ (seσ 7.3.3.1)«

ááIµ ORDERE─ QUEU┼ TA╟ message≤ arσ used¼ thσ targe⌠ shal∞ executσ thσ ì
command≤ iε thσ orde≥ receiveΣ witΦ respec⌠ t∩ othe≥ command≤ receiveΣ witΦ ì
ORDERE─ QUEU┼ TA╟ messages«  Al∞ command≤ receiveΣ witΦ aε SIMPL┼ QUEU┼ TA╟ ì
messagσ prio≥ t∩ ß commanΣ receiveΣ witΦ aε ORDERE─ QUEU┼ TA╟ message¼ ì
regardles≤ oµ initiator¼ shal∞ bσ executeΣ beforσ tha⌠ commanΣ witΦ thσ ì
ORDERE─ QUEU┼ TA╟ message«  Al∞ command≤ receiveΣ witΦ aε SIMPL┼ QUEU┼ TA╟ ì
messagσ afte≥ ß commanΣ receiveΣ witΦ aε ORDERE─ QUEU┼ TA╟ message¼ regardles≤ ì
oµ initiator¼ shal∞ bσ executeΣ afte≥ tha⌠ commanΣ witΦ thσ ORDERE─ QUEU┼ TA╟ ì
message«

áá┴ commanΣ receiveΣ witΦ ß HEA─ O╞ QUEU┼ TA╟ messagσ i≤ placeΣ firs⌠ iε thσ ì
queue¼ t∩ bσ executeΣ next«  ┴ commanΣ receiveΣ witΦ ß HEA─ O╞ QUEU┼ TA╟ ì
messagσ shal∞ no⌠ suspenΣ aε I/╧ proces≤ fo≥ whicΦ thσ targe⌠ ha≤ beguε ì
execution«  Consecutivσ command≤ receiveΣ witΦ HEA─ O╞ QUEU┼ TA╟ message≤ arσ ì
executeΣ iε ß las⌠-iε-firs⌠-ou⌠ order.

.cp 3
ááAε I/╧ proces≤ receiveΣ withou⌠ ß queuσ taτ messagσ whilσ therσ arσ an∙ ì
taggeΣ I/╧ command≤ iε thσ commanΣ queuσ froφ thσ samσ initiato≥ i≤ aε ì
incorrec⌠ initiato≥ connectioε (seσ 6.5.2⌐ unles≤ therσ i≤ ß contingen⌠ ì
allegiancσ o≥ extendeΣ contingen⌠ allegiancσ condition.

.cp 5èáá┴ serie≤ oµ linkeΣ command≤ arσ ß singlσ I/╧ process¼ anΣ arσ assigneΣ thσ ì
queuσ taτ establisheΣ iε thσ initia∞ connection«  ┴ commanΣ receiveΣ witΦ ß ì
HEA─ O╞ QUEU┼ TA╟ messagσ shal∞ no⌠ suspenΣ ß serie≤ oµ linkeΣ command≤ fo≥ ì
whicΦ thσ targe⌠ ha≤ beguε execution.

.cp 4
ááThσ RESERV┼ anΣ RELEAS┼ command≤ shoulΣ bσ sen⌠ witΦ aε ORDERE─ QUEU┼ TA╟ ì
message«  Usσ oµ thσ HEA─ O╞ QUEU┼ TA╟ messagσ witΦ thesσ command≤ coulΣ ì
resul⌠ iε reservatioε conflict≤ witΦ previousl∙ issueΣ commands«

ááThσ TES╘ UNI╘ READ┘ anΣ INQUIR┘ command≤ arσ ofteε sen⌠ witΦ ß HEA─ O╞ QUEU┼ ì
TA╟ message¼ sincσ thσ informatioε returneΣ ha≤ n∩ effec⌠ oε thσ conditioε oµ ì
thσ logica∞ unit«

ááTw∩ erro≥ recover∙ option≤ arσ allowed«  Thσ erro≥ recover∙ optioε t∩ bσ ì
useΣ i≤ specifieΣ iε thσ contro∞ modσ pagσ (seσ 7.3.3.1)«

ááThσ firs⌠ pos⌠-recover∙ optioε i≤ t∩ continuσ executioε oµ command≤ iε thσ ì
queuσ afte≥ thσ contingen⌠ allegiancσ o≥ extendeΣ contingen⌠ allegiancσ ì
conditioε ha≤ cleared«  Thσ targe⌠ return≤ BUS┘ statu≤ t∩ othe≥ initiator≤ ì
whilσ thσ contingen⌠ allegiancσ o≥ extendeΣ contingen⌠ allegiancσ conditioε ì
exists«  Durinτ thi≤ timσ al∞ command≤ iε thσ queuσ arσ suspended«  Al∞ ì
command≤ useΣ fo≥ recover∙ operation≤ shal∞ bσ untaggeΣ commands«  Thσ queuσ ì
ma∙ bσ modifieΣ b∙ removinτ al∞ o≥ selecteΣ command≤ iε thσ queuσ a≤ par⌠ oµ ì
thσ recover∙ procedure«

ááIµ command≤ arσ combineΣ b∙ thσ queuinτ algorithφ sucΦ tha⌠ thσ erro≥ ì
affect≤ morσ thaε onσ command¼ theε ß contingen⌠ allegiancσ conditioε shal∞ bσ ì
generateΣ fo≥ al∞ affecteΣ commands.

ááThσ seconΣ recover∙ optioε clear≤ thσ queuσ afte≥ thσ contingen⌠ allegiancσ ì
o≥ extendeΣ contingen⌠ allegiancσ conditioε ha≤ beeε cleared«  Wheε thσ queuσ ì
i≤ cleareΣ becausσ oµ thi≤ recover∙ option¼ ß uni⌠ attentioε conditioε shal∞ ì
bσ generateΣ fo≥ al∞ othe≥ initiator≤ anΣ thσ additiona∞ sensσ codσ shal∞ bσ ì
se⌠ t∩ COMMAND╙ CLEARE─ B┘ ANOTHE╥ INITIATOR.

.cp 3
ááDeferreΣ error≤ arσ normall∙ relateΣ t∩ ß commanΣ tha⌠ ha≤ alread∙ ì
completed«  A≤ such¼ therσ i≤ n∩ attemp⌠ t∩ returε thσ queuσ taτ valuσ ì
assigneΣ t∩ thσ origina∞ command.

.cp 5
áá┴ devicσ tha⌠ doe≤ no⌠ suppor⌠ taggeΣ queuinτ fo≥ an∙ reasoε (e.g.¼ no⌠ ì
implemented¼ disableΣ b∙ thσ DQuσ bi⌠ iε thσ contro∞ modσ page¼ o≥ i⌠ ha≤ beeε ì
switcheΣ t∩ aε operatinτ definitioε tha⌠ doe≤ no⌠ includσ taggeΣ queuing⌐ ì
shal∞ responΣ t∩ an∙ queuσ taτ messagσ witΦ ß MESSAG┼ REJEC╘ message«  Thσ ì
targe⌠ shal∞ continuσ thσ I/╧ proces≤ a≤ iµ i⌠ wa≤ aε untaggeΣ I/╧ process.

.cp 4
ááTaggeΣ queuinτ ma∙ als∩ bσ temporaril∙ disableΣ interna∞ t∩ thσ SCS╔ devicσ ì
durinτ certaiε initializatioε period≤ o≥ t∩ contro∞ interna∞ resourcσ ì
utilization«  Durinτ thesσ period≤ thσ targe⌠ ma∙ elec⌠ t∩ returε QUEU┼ FUL╠ ì
statu≤ o≥ i⌠ ma∙ responΣ t∩ an∙ queuσ taτ messagσ witΦ ß MESSAG┼ REJEC╘ ì
message.

.cp 5èááSevera∞ message≤ ma∙ bσ useΣ t∩ clea≥ par⌠ o≥ al∞ oµ thσ commanΣ queue«  ì
Pleasσ refe≥ t∩ thσ ABORT¼ ABOR╘ TAG¼ BU╙ DEVIC┼ RESET¼ anΣ CLEA╥ QUEU┼ ì
message≤ iε Sectioε ╡ fo≥ details.

.cp 10
.aw off
.pm 0
6.8.3. Examplσ oµ QueueΣ I/O Process
.aw on
.pm 3

ááAε examplσ oµ I/╧ proces≤ queuinτ benefit≤ froφ thσ consideratioε oµ thσ ì
executioε oµ ß numbe≥ oµ commands«  Afte≥ eacΦ command¼ thσ statσ oµ thσ queuσ ì
kep⌠ iε thσ targe⌠ i≤ showε t∩ indicatσ thσ functioε actuall∙ performeΣ b∙ thσ ì
queuing.

.cp 5
.aw off
.pm 0
6.8.3.1. Typica∞ Sequence≤ fo≥ TaggeΣ Queuing
.aw on
.pm 3
ááAε I/╧ proces≤ usinτ taggeΣ queuinτ use≤ thσ followinτ sequence≤ fo≥ norma∞ ì
execution«  Thσ initiato≥ firs⌠ arbitrate≤ fo≥ thσ SCS╔ bus¼ anΣ afte≥ ì
successfull∙ obtaininτ thσ SCS╔ bus¼ select≤ thσ appropriatσ SCS╔ device«  Thσ ì
AT╬ signa∞ i≤ asserteΣ durinτ thσ SELECTIO╬ phasσ t∩ indicatσ tha⌠ ß MESSAG┼ ì
OU╘ phasσ i≤ requesteΣ b∙ thσ initiator«  Thσ firs⌠ messagσ bytσ transferreΣ ì
i≤ aε IDENTIF┘ message«  Thσ AT╬ signa∞ continue≤ t∩ bσ asserteΣ durinτ thσ ì
MESSAG┼ OU╘ phasσ t∩ indicatσ tha⌠ thσ initiato≥ ha≤ anothe≥ message«  Thσ ì
seconΣ messagσ bytσ transferreΣ i≤ thσ firs⌠ bytσ oµ thσ appropriatσ queuσ taτ ì
message¼ iε thi≤ casσ ß SIMPL┼ QUEU┼ TA╟ message«  Thσ thirΣ anΣ las⌠ messagσ ì
bytσ i≤ transmitteΣ containinτ thσ seconΣ bytσ oµ thσ queuσ taτ message¼ thσ ì
queuσ tag«  A≤ i⌠ i≤ transferred¼ thσ AT╬ signa∞ i≤ negateΣ t∩ indicatσ tha⌠ ì
n∩ morσ messagσ byte≤ arσ available«  Thσ targe⌠ theε transfer≤ thσ commanΣ ì
descripto≥ block«  Assuminτ thσ commanΣ require≤ disconnection¼ thσ targe⌠ ì
transmit≤ ß DISCONNEC╘ messagσ t∩ thσ initiato≥ anΣ theε enter≤ thσ BU╙ FRE┼ ì
phase«  Thσ targe⌠ place≤ thσ command¼ identifieΣ b∙ thσ I_T_L_╤ nexus¼ a⌠ thσ ì
appropriatσ placσ iε thσ commanΣ queue.

ááWheε thσ targe⌠ remove≤ I/╧ processe≤ froφ thσ queuσ fo≥ execution¼ ß ì
physica∞ latenc∙ perioΣ ma∙ occur«  A⌠ thσ enΣ oµ thi≤ period¼ wheε thσ targe⌠ ì
i≤ prepareΣ t∩ transfe≥ thσ appropriatσ data¼ thσ targe⌠ begin≤ aε ARBITRATIO╬ ì
phasσ and¼ upoε winning¼ enter≤ ß RESELECTIO╬ phase«  Afte≥ ß successfu∞ ì
reselection¼ thσ targe⌠ send≤ thσ IDENTIF┘ messagσ followeΣ b∙ ß SIMPL┼ QUEU┼ ì
TA╟ messagσ witΦ thσ queuσ taτ valuσ originall∙ sen⌠ b∙ thσ initiator«  Thσ ì
initiato≥ use≤ thσ I_T_L_╤ nexu≤ t∩ identif∙ thσ correc⌠ se⌠ oµ pointer≤ anΣ ì
contro∞ block≤ associateΣ witΦ thσ I/╧ proces≤ anΣ t∩ establisΦ thσ necessar∙ ì
condition≤ fo≥ datß transfer«  Thσ targe⌠ begin≤ datß transfer«  Wheε thσ datß ì
transfe≥ i≤ successfull∙ completed¼ thσ targe⌠ return≤ GOO─ statu≤ anΣ ì
terminate≤ thσ I/╧ proces≤ witΦ ß COMMAN─ COMPLET┼ message.

.cp 5
.aw off
.pm 0
6.8.3.2. Examplσ oµ TaggeΣ Queuinτ 
.aw on
.pm 3
ááAε examplσ oµ thσ executioε oµ fivσ queueΣ I/╧ processe≤ i≤ describeΣ t∩ ì
demonstratσ ho≈ taggeΣ queuinτ operates«  Al∞ taggeΣ I/╧ processe≤ arσ froφ ì
onσ initiato≥ t∩ ß singlσ logica∞ uni⌠ oµ ß singlσ target«  Thσ fivσ I/╧ ì
processe≤ arσ defineΣ iε Tablσ ╢-8«  Thσ targe⌠ i≤ ß direc⌠-acces≤ device«  A⌠ ì
thσ timσ thσ I/╧ processe≤ arσ firs⌠ beinτ executed¼ i⌠ i≤ assumeΣ tha⌠ thσ ì
actuato≥ i≤ iε positioε t∩ acces≤ logica∞ blocδ 10000.

.cp 15è.aw off
.pm 0
               Table 6-8: Command≤ iε Orde≥ ReceiveΣ b∙ Target

                                   Queue  Logical
                                    Tag    Blocδ   Transfer
       CommanΣ  Queuσ Taτ Message  Value  Addres≤   LengtΦ     Status
       ------¡  -----------------  -----  ------¡  ---------  ---------
        REA─          SIMPL┼        0▒h    1000░     1000      QueueΣ
        REA─          SIMPL┼        0▓h      10░        1      Queued
        REA─         ORDERE─        0│h     100░     1000      Queued
        REA─          SIMPL┼        0┤h    1000░        ▒      Queued
        REA─          SIMPL┼        0╡h     200░     1000      QueueΣ
.aw on
.pm 3

ááThσ optimuφ orde≥ woulΣ requirσ tha⌠ thosσ block≤ closσ t∩ thσ actuato≥ ì
positioε bσ thσ firs⌠ block≤ accessed¼ followeΣ b∙ thosσ increasingl∙ fa≥ froφ ì
thσ actuato≥ position«  However¼ thσ commanΣ witΦ queuσ taτ 03Φ i≤ aε ordereΣ ì
I/╧ process¼ s∩ tha⌠ al∞ simplσ I/╧ processe≤ transferreΣ previousl∙ mus⌠ bσ ì
executeΣ before¼ whilσ al∞ simplσ I/╧ processe≤ transferreΣ afte≥ thσ ordereΣ ì
I/╧ proces≤ mus⌠ bσ executeΣ afte≥ thσ ordereΣ I/╧ process.

ááIµ ß targe⌠ support≤ aε optimizinτ algorithφ thσ actua∞ orde≥ iε whicΦ thσ ì
I/╧ processe≤ arσ executeΣ coulΣ bσ a≤ showε iε Tablσ ╢-9.

.cp 15
.aw off
.pm 1
                  Table 6-9: Command≤ iε Orde≥ oµ Execution

                                   Queue  Logical
                                    Tag    Blocδ   Transfer
       CommanΣ  Queuσ Taτ Message  Value  Addres≤   LengtΦ     Status
       ------¡  -----------------  -----  ------¡  ---------  ---------
        REA─          SIMPL┼        0▒h    1000░     1000      QueueΣ
        REA─          SIMPL┼        0▓h      10░        1      Queued
        REA─         ORDERE─        0│h     100░     1000      Queued
        REA─          SIMPL┼        0╡h     200░     1000      QueueΣ
        REA─          SIMPL┼        0┤h    1000░        ▒      Queued
.aw on
.pm 3


.cp 9
ááI/╧ processe≤ witΦ queuσ taτ value≤ 01Φ anΣ 02Φ arσ executeΣ iε thσ orde≥ ì
receiveΣ sincσ thσ actuato≥ i≤ alread∙ iε positioε t∩ executσ I/╧ proces≤ 01h«  ì
I/╧ proces≤ 02Φ mus⌠ bσ executeΣ beforσ I/╧ proces≤ 04Φ o≥ 05Φ becausσ thσ ì
ordereΣ I/╧ proces≤ 03Φ wa≤ transmitteΣ afte≥ I/╧ processe≤ 01Φ anΣ 02Φ bu⌠ ì
beforσ I/╧ processe≤ 04Φ anΣ 05h«  I/╧ proces≤ 03Φ i≤ theε executeΣ afte≥ I/╧ ì
proces≤ 02h«  Thσ I/╧ processe≤ 04Φ anΣ 05Φ arσ executeΣ afte≥ thσ ordereΣ I/╧ ì
proces≤ 03h«  I/╧ proces≤ 05Φ i≤ executeΣ beforσ I/╧ proces≤ 04Φ becausσ thσ ì
actuato≥ i≤ iε positioε t∩ acces≤ blocδ 200░ afte≥ executinτ I/╧ proces≤ 03h«  ì
I/╧ proces≤ 04Φ i≤ executeΣ last«

.cp 8
ááA≤ aε examplσ oµ thσ operatioε oµ thσ HEA─ O╞ QUEU┼ TA╟ I/╧ process¼ ì
conside≥ tha⌠ ß ne≈ I/╧ process¼ identifieΣ b∙ ß HEA─ O╞ QUEU┼ TA╟ messagσ ì
witΦ ß queuσ taτ oµ 08h¼ i≤ transmitteΣ t∩ thσ targe⌠ whilσ thσ ordereΣ I/╧ ì
proces≤ 03Φ i≤ beinτ executed«  Thσ I/╧ proces≤ 03Φ continue≤ execution¼ bu⌠ ì
thσ ne≈ HEA─ O╞ QUEU┼ TA╟ I/╧ proces≤ i≤ placeΣ iε thσ queuσ fo≥ executioε ì
beforσ al∞ subsequen⌠ I/╧ processes«  Iε thi≤ case¼ thσ queuσ fo≥ executioε ì
afte≥ thσ ordereΣ I/╧ proces≤ 03Φ wa≤ executeΣ woulΣ appea≥ a≤ showε iε Tablσ ì
╢-10.

è.cp 15
.aw off
.pm 1
              Table 6-10: ModifieΣ b∙ HEA─ O╞ QUEU┼ TA╟ Message

                                   Queue  Logical
                                    Tag    Blocδ   Transfer
       CommanΣ  Queuσ Taτ Message  Value  Addres≤   LengtΦ     Status
       ------¡  -----------------  -----  ------¡  --------¡  ---------
        REA─         ORDERE─        0│h     100░      100░    Executing
        REA─      HEA─ O╞ QUEU┼     08Φ        ░         ╕     Queued
        REA─          SIMPL┼        0╡h     200░      1000     Queued
        REA─          SIMPL┼        0┤h    1000░         1     QueueΣ
.aw on
.pm 3

ááT∩ obtaiε maximuφ performancσ gain≤ usinτ taggeΣ queuinτ require≤ carefu∞ ì
implementatioε oµ thσ queuinτ algorithm≤ iε thσ target«  Iε addition¼ ì
initiator≤ shoulΣ allo≈ ß maximuφ numbe≥ oµ simplσ I/╧ processe≤ t∩ bσ ì
executeΣ witΦ ß minimuφ numbe≥ oµ ordereΣ I/╧ processes«  RESERV┼ anΣ RELEAS┼ ì
commands¼ SE╘ LIMIT╙ commands¼ anΣ appropriatσ softwarσ lockinτ convention≤ ì
shoulΣ bσ useΣ t∩ guaranteσ thσ prope≥ relationshi≡ betweeε thσ command≤ ì
executeΣ anΣ thσ datß storeΣ oε thσ periphera∞ devices«  Thesσ convention≤ arσ ì
no⌠ defineΣ b∙ thi≤ standard.

.cp 10
.aw off
.pm 0
6.9. Uni⌠ Attentioε Condition
.aw on
.pm 3

ááThσ targe⌠ shal∞ generatσ ß uni⌠ attentioε conditioε fo≥ eacΦ initiato≥ oε ì
eacΦ valiΣ logica∞ uni⌠ wheneve≥ thσ targe⌠ ha≤ beeε rese⌠ b∙ ß BU╙ DEVIC┼ ì
RESE╘ message¼ ß harΣ rese⌠ condition¼ o≥ b∙ ß powe≥-oε reset«  Thσ targe⌠ ì
shal∞ als∩ generatσ ß uni⌠ attentioε conditioε oε thσ affecteΣ logica∞ unit(s⌐ ì
fo≥ eacΦ initiato≥ wheneve≥ onσ oµ thσ followinτ event≤ occurs:
.lm 3
áá(1⌐ ┴ removablσ mediuφ ma∙ havσ beeε changed.
áá(2⌐ Thσ modσ parameter≤ iε effec⌠ fo≥ thi≤ initiato≥ havσ beeε changeΣ b∙ ì
ááanothe≥ initiator.
áá(3⌐ Thσ versioε o≥ leve∞ oµ microcodσ ha≤ beeε changed.
áá(4⌐ TaggeΣ command≤ queueΣ fo≥ thi≤ initiato≥ werσ cleareΣ b∙ anothe≥ ì
ááinitiator.
áá(5⌐ INQUIR┘ datß ha≤ beeε changed.
áá(6⌐ Thσ modσ parameter≤ iε effec⌠ fo≥ thi≤ initiato≥ havσ beeε restoreΣ froφ ì
áánoε-volatilσ memory.
áá(7⌐ ┴ changσ iε thσ conditioε oµ ß synchronizeΣ spindle.
áá(8⌐ An∙ othe≥ even⌠ occur≤ tha⌠ require≤ thσ attentioε oµ thσ initiator.
.lm 1

.pm 0
.lm 3
ááIMPLEMENTOR╙ NOTES:
áá(1⌐  Target≤ ma∙ queuσ uni⌠ attentioε condition≤ oε logica∞ units«  Afte≥ ì
ááthσ firs⌠ uni⌠ attentioε conditioε i≤ cleared¼ anothe≥ uni⌠ attentioε ì
ááconditioε ma∙ exis⌠ (e.g.¼ ß powe≥ oε conditioε followeΣ b∙ ß microcodσ ì
ááchangσ condition)«  Thσ initiato≥ caε clea≥ al∞ pendinτ uni⌠ attentioε ì
áácondition≤ b∙ repeatedl∙ sendinτ thσ REQUES╘ SENS┼ commanΣ unti∞ ß sensσ ke∙ ì
ááothe≥ thaε UNI╘ ATTENTIO╬ i≤ returneΣ b∙ thσ target.
áá(2⌐  Seσ 6.5.│ fo≥ requirement≤ concerninτ selectioε oµ aε invaliΣ logica∞ ì
ááunit.
.pm 3
.lm 1

.cp 3
ááThσ uni⌠ attentioε conditioε shal∞ persis⌠ oε thσ logica∞ uni⌠ fo≥ eacΦ ì
initiato≥ unti∞ tha⌠ initiato≥ clear≤ thσ conditioε a≤ describeΣ iε thσ ì
followinτ paragraphs.

.cp 7èááIµ aε INQUIR┘ commanΣ i≤ receiveΣ froφ aε initiato≥ t∩ ß logica∞ uni⌠ witΦ ß ì
pendinτ uni⌠ attentioε conditioε (beforσ thσ targe⌠ generate≤ thσ contingen⌠ ì
allegiancσ condition)¼ thσ targe⌠ shal∞ perforφ thσ INQUIR┘ commanΣ anΣ shal∞ ì
no⌠ clea≥ thσ uni⌠ attentioε condition«  Iµ thσ INQUIR┘ commanΣ i≤ receiveΣ ì
afte≥ thσ targe⌠ ha≤ generateΣ thσ contingen⌠ allegiancσ conditioε fo≥ ß ì
pendinτ uni⌠ attentioε condition¼ theε thσ uni⌠ attentioε conditioε oε thσ ì
logica∞ uni⌠ shal∞ bσ cleared¼ anΣ thσ targe⌠ shal∞ perforφ thσ INQUIR┘ ì
command.

ááIµ an∙ othe≥ commanΣ i≤ receiveΣ afte≥ thσ targe⌠ ha≤ generateΣ thσ ì
contingen⌠ allegiancσ conditioε fo≥ ß pendinτ uni⌠ attentioε condition¼ thσ ì
uni⌠ attentioε conditioε oε thσ logica∞ uni⌠ shal∞ bσ cleared¼ anΣ iµ n∩ othe≥ ì
uni⌠ attentioε conditioε i≤ pendinτ thσ targe⌠ shal∞ perforφ thσ command«  Iµ ì
anothe≥ uni⌠ attentioε conditioε i≤ pendinτ thσ targe⌠ shal∞ no⌠ perforφ thσ ì
commanΣ anΣ shal∞ generatσ anothe≥ contingen⌠ allegiancσ condition.

ááIµ ß REQUES╘ SENS┼ commanΣ i≤ receiveΣ froφ aε initiato≥ witΦ ß pendinτ uni⌠ ì
attentioε conditioε (beforσ thσ targe⌠ generate≤ thσ contingen⌠ allegiancσ ì
condition)¼ theε thσ targe⌠ ma∙ either:
.cp 2
áá(1⌐ repor⌠ an∙ pendinτ sensσ datß anΣ preservσ thσ uni⌠ attentioε conditioε ì
oε thσ logica∞ uni⌠ or
.cp 2
áá(2⌐ repor⌠ thσ uni⌠ attentioε condition¼ ma∙ discarΣ an∙ pendinτ sensσ data¼ ì
anΣ clea≥ thσ uni⌠ attentioε conditioε oε thσ logica∞ uni⌠ fo≥ tha⌠ initiator.

ááIµ thσ targe⌠ ha≤ alread∙ generateΣ thσ contingen⌠ allegiancσ conditioε fo≥ ì
thσ uni⌠ attentioε condition¼ thσ targe⌠ shal∞ perforφ thσ seconΣ actioε ì
listeΣ above.

ááIµ aε initiato≥ issue≤ ß commanΣ othe≥ thaε INQUIR┘ o≥ REQUES╘ SENS┼ whilσ ß ì
uni⌠ attentioε conditioε exist≤ fo≥ tha⌠ initiato≥ (prio≥ t∩ generatinτ thσ ì
contingen⌠ allegiancσ conditioε fo≥ thσ uni⌠ attentioε condition)¼ thσ targe⌠ ì
shal∞ no⌠ perforφ thσ commanΣ anΣ shal∞ repor⌠ CHEC╦ CONDITIO╬ statu≤ unles≤ ß ì
highe≥ priorit∙ statu≤ a≤ defineΣ b∙ thσ targe⌠ i≤ als∩ pendinτ (e.g.¼ BUS┘ o≥ ì
RESERVATIO╬ CONFLICT).

.cp 5
ááIµ afte≥ generatinτ thσ contingen⌠ allegiancσ conditioε fo≥ ß pendinτ uni⌠ ì
attentioε condition¼ thσ nex⌠ commanΣ receiveΣ froφ tha⌠ initiato≥ oε thσ ì
logica∞ uni⌠ i≤ no⌠ REQUES╘ SENSE¼ theε tha⌠ commanΣ shal∞ bσ performeΣ anΣ ì
thσ uni⌠ attentioε conditioε shal∞ bσ cleareΣ fo≥ tha⌠ initiato≥ oε thσ ì
logica∞ uni⌠ anΣ thσ sensσ datß i≤ los⌠ (seσ 6.6).

ááIµ ß targe⌠ become≤ ß temporar∙ initiato≥ t∩ issuσ ß SEN─ commanΣ witΦ aε ì
AE╬ bi⌠ oµ one¼ whicΦ inform≤ thσ initiato≥ (temporar∙ target⌐ oµ thσ uni⌠ ì
attentioε condition¼ anΣ thσ SEN─ commanΣ complete≤ witΦ GOO─ status¼ theε thσ ì
targe⌠ shal∞ clea≥ thσ uni⌠ attentioε conditioε fo≥ tha⌠ initiato≥ oε thσ ì
logica∞ uni⌠ (seσ 6.5.5).

..end of section
.paè




















áá                     (Thi≤ pagσ i≤ intentionall∙ blank.)
.paè