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.fo Section 9 # 9. Group 0 Command Descriptions for Sequential-Access Devices The Group 0 commands for sequential-access devices shall be as shown in Table9-1. Table 9-1 Group 0 Commands for Sequential-Access Devices ============================================================================== Operation Code Type Command Name Section ------------------------------------------------------------------------------ 00H O TEST UNIT READY 7.1.1 01H M REWIND 9.1 02H V 03H M REQUEST SENSE 7.1.2 04H R 05H E READ BLOCK LIMITS 9.2 06H V 07H V 08H M READ 9.3 09H V 0AH M WRITE 9.4 0BH O TRACK SELECT 9.5 0CH V 0DH V 0EH V 0FH O READ REVERSE 9.6 10H M WRITE FILEMARKS 9.7 11H O SPACE 9.8 12H E INQUIRY 7.1.3 13H O VERIFY 9.9 14H O RECOVER BUFFERED DATA 9.10 15H O MODE SELECT 9.11 16H O RESERVE UNIT 9.12.1 17H O RELEASE UNIT 9.12.2 18H O COPY 7.1.4 19H O ERASE 9.13 1AH O MODE SENSE 9.14 1BH O LOAD/UNLOAD 9.15 1CH O RECEIVE DIAGNOSTIC RESULTS 7.1.5 1DH O SEND DIAGNOSTIC 7.1.6 1EH O PREVENT/ALLOW MEDIUM REMOVAL 9.16 1FH R ============================================================================== Key: M = Command implementation is mandatory. E = Command implementation is required for SCSI devices that support device-independent self-configuring software. O = Command implementation is optional. R = Operation code is reserved for future standardization. V = Operation code is available for vendor unique commands. .pa 9.1 REWIND Command Peripheral Device Type: Sequential Access Operation Code Type: Mandatory Operation Code: 01H Table 9-2 REWIND Command ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code | -----|-----------------------------------------------------------------------| 1 | Logical Unit Number | Reserved | Immed | -----|-----------------------------------------------------------------------| 2 | Reserved | -----|-----------------------------------------------------------------------| 3 | Reserved | -----|-----------------------------------------------------------------------| 4 | Reserved | -----|-----------------------------------------------------------------------| 5 | Vendor Unique | Reserved | Flag | Link | ============================================================================== The REWIND command (Table 9-2) requests that the target rewind the logical unit to the beginning-of-medium or load-point. An immediate (Immed) bit of one indicates that status shall be returned as soon as the operation is initiated. An Immed bit of zero indicates that status shall be returned after the operation is completed. .pa 9.2 READ BLOCK LIMITS Command Peripheral Device Type: Sequential Access Operation Code Type: Extended Operation Code: 05H Table 9-3 READ BLOCK LIMITS Command ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code | -----|-----------------------------------------------------------------------| 1 | Logical Unit Number | Reserved | -----|-----------------------------------------------------------------------| 2 | Reserved | -----|-----------------------------------------------------------------------| 3 | Reserved | -----|-----------------------------------------------------------------------| 4 | Reserved | -----|-----------------------------------------------------------------------| 5 | Vendor Unique | Reserved | Flag | Link | ============================================================================== The READ BLOCK LIMITS command (Table 9-3) requests that the target's capability for block length limits be returned for the logical unit. The READ BLOCK LIMITS data shown in Table 9-4 shall be sent during the DATA IN phase of the command. Table 9-4 READ BLOCK LIMITS Data ============================================================================== Byte | Description | ============================================================================== 0 | Reserved | -----|-----------------------------------------------------------------------| 1 | Maximum Block Length (MSB) | -----|-----------------------------------------------------------------------| 2 | Maximum Block Length | -----|-----------------------------------------------------------------------| 3 | Maximum Block Length (LSB) | -----|-----------------------------------------------------------------------| 4 | Minimum Block Length (MSB) | -----|-----------------------------------------------------------------------| 5 | Minimum Block Length (LSB) | ============================================================================== If the maximum block length equals the minimum block length, only fixed- length blocks of the length indicated are supported. Otherwise, variable- length blocks are supported. For variable-length blocks, if the maximum block length equals zero, no upper limit is specified. .pa 9.3 READ Command Peripheral Device Type: Sequential Access Operation Code Type: Mandatory Operation Code: 08H Table 9-5 READ Command ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code | -----|-----------------------------------------------------------------------| 1 | Logical Unit Number | Reserved | Fixed | -----|-----------------------------------------------------------------------| 2 | Transfer Length (MSB) | -----|-----------------------------------------------------------------------| 3 | Transfer Length | -----|-----------------------------------------------------------------------| 4 | Transfer Length (LSB) | -----|-----------------------------------------------------------------------| 5 | Vendor Unique | Reserved | Flag | Link | ============================================================================== The READ command (Table 9-5) transfers one or more block(s) to the initiator beginning with the next block on the logical unit. The fixed bit specifies both the meaning of the transfer length field and whether fixed-length or variable-length block(s) are to be transferred. If the fixed bit is zero, a single block shall be transferred with the transfer length specifying the maximum number of bytes the initiator has allocated for the returned data. If the actual block length is different from the specified transfer length, a CHECK CONDITION status shall be sent to the initiator and the incorrect length indicator (ILI) bit and valid bit in extended sense shall be set to one. The information bytes in extended sense shall be set to the difference (residue) between the requested transfer length and the actual block length. Targets that do not support negative residues shall set the ILI bit to one and the residue to zero when the actual block length is larger than the transfer length. In any case, no more than transfer length bytes shall be transferred to the initiator and the medium shall be positioned after the block (end-of-medium side). If the fixed bit is one, the transfer length specifies the number of blocks to be transferred to the initiator. This form of the READ command is valid only if the logical unit is currently operating in fixed block mode. A logical unit is in fixed block mode when either of the following conditions are true: (1) The logical unit reports the same value for minimum block length and maximum block length in response to the READ BLOCK LIMITS command. In this case, the current block length is the value returned. (2) The logical unit unit has been instructed to use fixed-length blocks with the MODE SELECT command. In this case, the current block length is the block length defined in the MODE SELECT command. Otherwise, the logical unit is in variable block mode. The target may implement fixed block mode, variable block mode, or both modes. If the fixed bit does not match the current mode, or the mode indicated by the fixed bit is not implemented, the target shall reject the command by returning a CHECK CONDITION status and by setting the sense key to ILLEGAL REQUEST. A successful READ command with the fixed bit equal to one shall transfer the current block length times the transfer length bytes of data to the initiator. Upon termination of the READ command, the medium shall be positioned after the last block transferred (end-of-medium side). If the fixed bit is one and if a block is read that is larger or smaller than the current block length, a CHECK CONDITION status shall be returned to the initiator. The ILI bit and the valid bit in extended sense shall be set to one. The information bytes shall be set to the difference (residue) between the requested transfer length and the actual number of blocks read (not including the incorrect length block). Upon termination, the medium shall be positioned after the incorrect length block (end-of-medium side). If a logical unit reads a filemark during a READ command, it shall send a CHECK CONDITION status to the initiator and shall set the filemark bit in extended sense. Upon termination, the medium shall be positioned after the filemark (end-of-medium side). If the fixed bit is one, the target shall set the valid bit to one and the information bytes shall be set to the difference (residue) between the requested transfer length and the actual number of blocks read (not including the filemark). If a logical unit encounters the physical end-of-medium during a READ command, the target shall return a CHECK CONDITION status to the initiator and shall set the end-of-medium (EOM) bit to one in extended sense. The sense key shall be set to MEDIUM ERROR. If the fixed bit is one, the target shall set the valid bit to one and the information bytes to the difference (residue) between the requested transfer length and the actual number of blocks successfully read. The medium position following this condition is not defined. When the transfer length is zero, no data shall be transferred and the current position on the logical unit shall not be changed. This condition shall not be considered as an error. .pa 9.4 WRITE Command Peripheral Device Type: Sequential Access Operation Code Type: Mandatory Operation Code: 0AH Table 9-6 WRITE Command ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code | -----|-----------------------------------------------------------------------| 1 | Logical Unit Number | Reserved | Fixed | -----|-----------------------------------------------------------------------| 2 | Transfer Length (MSB) | -----|-----------------------------------------------------------------------| 3 | Transfer Length | -----|-----------------------------------------------------------------------| 4 | Transfer Length (LSB) | -----|-----------------------------------------------------------------------| 5 | Vendor Unique | Reserved | Flag | Link | ============================================================================== The WRITE command (Table 9-6) transfers one or more block(s) from the initiator to the current position on the logical unit. The fixed bit specifies both the meaning of the transfer length field and whether fixed- length or variable-length block(s) are to be transferred. If the fixed bit is zero, a single block shall be transferred from the initiator and shall be written to the logical unit beginning at the current medium position. The transfer length specifies the length of the block to be written (in bytes). The requested block length shall be within the minimum and maximum block length range (returned by the READ BLOCK LIMITS command, Section 9.2). If this condition is not met, a CHECK CONDITION status shall be returned and the sense key shall be set to ILLEGAL REQUEST and no data shall be written. Upon successful termination, the medium shall be positioned after the block written by this command (end-of-medium side). If the fixed bit is one, the transfer length field specifies the number of block(s) to be transferred to the logical unit beginning at the current medium position. This form of the WRITE command is valid only if the logical unit is currently operating in fixed block mode (see 9.3). Upon termination, the medium shall be positioned after the block(s) written by this command (end-of- medium side) The target may implement fixed block mode, variable block mode, or both modes. If the fixed bit does not match the current mode, or the mode indicated by the fixed bit is not implemented, the target shall reject the command by returning a CHECK CONDITION status and by setting the sense key to ILLEGAL REQUEST. If the early warning end-of-medium condition is encountered while writing, an attempt to finish writing any buffered data may be made. The command shall terminate with a CHECK CONDITION status and the EOM bit in extended sense shall be set to one. If any data remains in the target's buffer, then the sense key shall be set to VOLUME OVERFLOW. If the fixed bit is one and the logical unit is not buffered (buffered mode of the MODE SENSE command is zero), then the valid bit in extended sense shall be set to one and the information bytes shall be set to the difference (residue) between the requested transfer length and the actual number of blocks written to the medium. If the fixed bit is one and the logical unit is buffered (buffered mode of the MODE SENSE command is one), then the valid bit shall be set to one and the information bytes shall be set to the total number of blocks not written (the number of blocks not transferred from the initiator plus the number of blocks remaining in the target's buffer). Note that in this case it is possible for the value in the information bytes to exceed the transfer length. When the transfer length is zero, no data shall be transferred and the current position on the logical unit shall not be changed. This condition shall not be considered as an error. 9.5 TRACK SELECT Command Peripheral Device Type: Sequential Access Operation Code Type: Optional Operation Code: 0BH Table 9-7 TRACK SELECT Command ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code | -----|-----------------------------------------------------------------------| 1 | Logical Unit Number | Reserved | -----|-----------------------------------------------------------------------| 2 | Reserved | -----|-----------------------------------------------------------------------| 3 | Reserved | -----|-----------------------------------------------------------------------| 4 | Track Value | -----|-----------------------------------------------------------------------| 5 | Vendor Unique | Reserved | Flag | Link | ============================================================================== The TRACK SELECT command (Table 9-7) requests that the track specified in the track value field be selected. .pa 9.6 READ REVERSE Command Peripheral Device Type: Sequential Access Operation Code Type: Optional Operation Code: 0FH Table 9-8 READ REVERSE Command ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code | -----|-----------------------------------------------------------------------| 1 | Logical Unit Number | Reserved | Fixed | -----|-----------------------------------------------------------------------| 2 | Transfer Length (MSB) | -----|-----------------------------------------------------------------------| 3 | Transfer Length | -----|-----------------------------------------------------------------------| 4 | Transfer Length (LSB) | -----|-----------------------------------------------------------------------| 5 | Vendor Unique | Reserved | Flag | Link | ============================================================================== The READ REVERSE command (Table 9-8) functions identically to the READ command except that medium motion is in the reverse direction. Thus, the block(s) and bytes within the block(s) are transferred in the reverse order and the medium position upon termination is before the last block read (beginning-of-medium side). This command shall terminate with a CHECK CONDITION status and the EOM bit in extended sense shall be set to one if beginning-of-medium or load-point is encountered. The sense key shall be set to NO SENSE. If the fixed bit is one, then the valid bit shall be set to one and the information bytes shall contain the difference (residue) of the requested transfer length and the actual number of blocks transferred before beginning-of-medium or load-point was encountered. Filemark handling is the same as in the READ command except that the medium position upon command termination shall be before the filemark (beginning-of- medium side). If the transfer length is zero, no data shall be transferred and the current position on the logical unit shall not be changed. This condition shall not be considered as an error. The target may implement fixed block mode, variable block mode, or both modes. If the fixed bit does not match the current mode, or the mode indicated by the fixed bit is not implemented, the target shall reject the command by returning a CHECK CONDITION status and by setting the sense key to ILLEGAL REQUEST. .pa 9.7 WRITE FILEMARKS Command Peripheral Device Type: Sequential Access Operation Code Type: Mandatory Operation Code: 10H Table 9-9 WRITE FILEMARKS Command ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code | -----|-----------------------------------------------------------------------| 1 | Logical Unit Number | Reserved | -----|-----------------------------------------------------------------------| 2 | Number of Filemarks (MSB) | -----|-----------------------------------------------------------------------| 3 | Number of Filemarks | -----|-----------------------------------------------------------------------| 4 | Number of Filemarks (LSB) | -----|-----------------------------------------------------------------------| 5 | Vendor Unique | Reserved | Flag | Link | ============================================================================== The WRITE FILEMARKS command (Table 9-9) causes the specified number of filemarks to be written beginning at the current medium position on the logical unit. A zero in this field indicates that no filemarks are to be written. This command is also used to force any buffered data (see buffered mode in the MODE SENSE command, Section 9.14) to be written. This command shall not return a GOOD status unless all buffered data blocks and the filemarks (if any) are correctly written on the medium. If the early warning end-of-medium condition is encountered while writing, an attempt to finish writing any buffered data may be made. The command shall terminate with a CHECK CONDITION status and the EOM bit in extended sense shall be set to one. If any filemarks remain to be written, then the sense key shall be set to VOLUME OVERFLOW. If the logical unit is not buffered (buffered mode of the MODE SENSE command is zero), then the valid bit in extended sense shall be set to one and the information bytes shall be set to the number of unwritten filemarks. If the logical unit is buffered (buffered mode of the MODE SENSE command is one), then the valid bit shall be set to one and the information bytes shall be set to the total number of blocks not written (the number of unwritten filemarks plus the number of blocks remaining in the target's buffer). Note that in this case it is possible for the value in the information bytes to exceed the transfer length. .pa 9.8 SPACE Command Peripheral Device Type: Sequential Access Operation Code Type: Optional Operation Code: 11H Table 9-10 SPACE Command ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code | -----|-----------------------------------------------------------------------| 1 | Logical Unit Number | Reserved | Code | -----|-----------------------------------------------------------------------| 2 | Count (MSB) | -----|-----------------------------------------------------------------------| 3 | Count | -----|-----------------------------------------------------------------------| 4 | Count (LSB) | -----|-----------------------------------------------------------------------| 5 | Vendor Unique | Reserved | Flag | Link | ============================================================================== The SPACE command (Table 9-10) provides a variety of positioning functions that are determined by the code and count. Both forward (toward end-of- medium) and reverse (toward beginning-of-medium) positioning are provided, although some SCSI devices may only support a subset of this command. Such SCSI devices shall return a CHECK CONDITION status and set the sense key to ILLEGAL REQUEST in response to any attempt to invoke a function that is not supported. The code is defined as follows: DB(1) DB(0) Description ----- ----- -------------------- 0 0 Blocks 0 1 Filemarks 1 0 Sequential Filemarks 1 1 Physical End-of-Data When spacing over blocks or filemarks, the count field specifies the number of blocks or filemarks to be spaced over. A positive value N in the count field shall cause forward medium movement over N blocks or filemarks ending on the end-of-medium side of the last block or filemark. A zero value in the count field shall cause no medium movement. A negative value -N (2's complement notation) in the count field shall cause reverse medium movement over N blocks or filemarks ending on the beginning-of-medium side of the last block or filemark. If a filemark is encountered while spacing over blocks, medium movement shall be stopped. The medium shall be positioned on the end-of-medium side of the filemark if movement was in the forward direction and on the beginning-of- medium side of the filemark if movement was in the reverse direction. A CHECK CONDITION status shall be sent to the initiator and the filemark and valid bits in extended sense shall be set to one. The information bytes shall be set to the difference (residue) in the requested count and the actual number of blocks spaced over (not including the filemark). If the physical end-of-medium is encountered while spacing forward over blocks or filemarks, the target shall return a CHECK CONDITION status to the initiator and shall set the end-of-medium (EOM) bit in extended sense to one. The sense key shall be set to MEDIUM ERROR. The target shall set the valid bit to one and the information bytes to the difference (residue) between the requested count and the actual number of blocks or filemarks spaced over. If beginning-of-medium or load-point is encountered while spacing over blocks or filemarks in the reverse direction, the target shall return a CHECK CONDITION status to the initiator and shall set the end-of-medium (EOM) bit in extended sense to one. The sense key shall be set to NO SENSE. The target shall set the valid bit to one and the information bytes to the difference (residue) between the requested count and the actual number of blocks or filemarks spaced over. When spacing over sequential filemarks, the count field is interpreted as follows: (1) A positive value N shall cause forward medium movement to the first occurrence of N or more consecutive filemarks stopping after the Nth filemark. (2) A zero value shall cause no medium movement. (3) A negative value -N (2's complement notation) shall cause reverse medium movement to the first occurrence of N or more consecutive filemarks stopping on the beginning-of-medium side of the Nth filemark. When spacing to physical end-of-data, the count field is ignored. Forward medium movement shall occur until the logical unit encounters physical end-of- data as defined by the sequential-access device. Some sequential-access devices define physical end-of-data as an erased area on the medium; however, other definitions are not precluded. Targets that implement this function shall leave the medium positioned such that a subsequent WRITE command would append data to the last recorded information on the medium. .pa 9.9 VERIFY Command Peripheral Device Type: Sequential Access Operation Code Type: Optional Operation Code: 13H Table 9-11 VERIFY Command ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code | -----|-----------------------------------------------------------------------| 1 | Logical Unit Number | Reserved | BytCmp | Fixed | -----|-----------------------------------------------------------------------| 2 | Verification Length (MSB) | -----|-----------------------------------------------------------------------| 3 | Verification Length | -----|-----------------------------------------------------------------------| 4 | Verification Length (LSB) | -----|-----------------------------------------------------------------------| 5 | Vendor Unique | Reserved | Flag | Link | ============================================================================== The VERIFY command (Table 9-11) verifies one or more block(s) beginning with the next block on the logical unit. The fixed bit specifies both the meaning of the verification length field and whether fixed-length or variable-length block(s) are to be verified. A byte compare (BytCmp) bit of zero indicates that the verification shall be simply a medium verification (CRC, ECC, etc). No data shall be transferred between the initiator and target. A byte compare bit of one indicates that a byte-by-byte compare of the data on the medium, and the data transferred from the initiator shall be performed by the target. Data shall be transferred >From the initiator to the target as in a WRITE command. A fixed bit of zero requests that the next block of the logical unit be verified. The verification length specifies the number of bytes to verify. A fixed bit of one requests verification length blocks be verified beginning with the next logical block on the logical unit. This form of the VERIFY command is only valid if the logical unit is currently in fixed block mode as defined in the READ command. If the data does not compare (byte compare bit equals one), the command shall terminate with a CHECK CONDITION status and the sense key shall be set to MISCOMPARE. If the fixed bit is one, the valid bit shall be set to one and the information bytes shall be set to the difference (residue) between the verification length and the actual number of blocks successfully verified. The medium shall be positioned after the block containing the miscompare (end-of-medium side). The target may implement fixed block mode, variable block mode, or both modes. If the fixed bit does not match the current mode, or the mode indicated by the fixed bit is not implemented, the target shall reject the command by returning a CHECK CONDITION status and by setting the sense key to ILLEGAL REQUEST. The VERIFY command shall terminate when the verification length has been satisfied, when a filemark is encountered, or when physical end-of-medium is encountered. The status and sense data for each of these conditions are handled the same as in the READ command. Upon completion of the VERIFY command, the medium shall be positioned after the last block from which data was verified or after the filemark, if encountered. When the verification length is zero, no data shall be verified and the current position on the logical unit shall not be changed. This condition shall not be considered as an error. 9.10 RECOVER BUFFERED DATA Command Peripheral Device Type: Sequential Access Operation Code Type: Optional Operation Code: 14H Table 9-12 RECOVER BUFFERED DATA Command ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code | -----|-----------------------------------------------------------------------| 1 | Logical Unit Number | Reserved | Fixed | -----|-----------------------------------------------------------------------| 2 | Transfer Length (MSB) | -----|-----------------------------------------------------------------------| 3 | Transfer Length | -----|-----------------------------------------------------------------------| 4 | Transfer Length (LSB) | -----|-----------------------------------------------------------------------| 5 | Vendor Unique | Reserved | Flag | Link | ============================================================================== The RECOVER BUFFERED DATA command (Table 9-12) is used to read data that has been transferred to an SCSI device buffer but has not been written on the medium. It is normally only used to recover from error or exception conditions that make it impossible to write the buffered data on the medium. This command functions similarly to the READ command except that the data is transferred from the SCSI device buffer instead of the medium. The order in which block(s) are transferred is the same as if they would have been transferred to the medium. One or more RECOVER BUFFERED DATA commands may be used to read the unwritten buffered data. The target may implement fixed block mode, variable block mode, or both modes. If the fixed bit does not match the current mode, or the mode indicated by the fixed bit is not implemented, the target shall reject the command by returning a CHECK CONDITION status and by setting the sense key to ILLEGAL REQUEST. If an attempt is made to recover more logical blocks of data than are contained in the SCSI device buffer, the command shall be terminated with a CHECK CONDITION status. The EOM bit in extended sense shall be set to one. If the fixed bit is one, the valid bit shall be set to one and the information bytes shall be set to the difference (residue) between the requested transfer length and the actual number of blocks transferred. The transfer length specifies the number of contiguous logical blocks of data to be transferred. A transfer length of zero indicates that no data shall be transferred. This condition shall not be considered as an error. 9.11 MODE SELECT Command Peripheral Device Type: Sequential Access Operation Code Type: Optional Operation Code: 15H Table 9-13 MODE SELECT Command ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code | -----|-----------------------------------------------------------------------| 1 | Logical Unit Number | Reserved | -----|-----------------------------------------------------------------------| 2 | Reserved | -----|-----------------------------------------------------------------------| 3 | Reserved | -----|-----------------------------------------------------------------------| 4 | Parameter List Length | -----|-----------------------------------------------------------------------| 5 | Vendor Unique | Reserved | Flag | Link | ============================================================================== The MODE SELECT command (Table 9-13) provides a means for the initiator to specify medium, logical unit, or peripheral device parameters to the target. The parameter list length specifies the length in bytes of the MODE SELECT parameter list that shall be transferred during the DATA OUT phase. A zero parameter list length indicates that no data shall be transferred. This condition shall not be considered as an error. The MODE SELECT parameter list shown in Table 9-14 contains a four-byte header, followed by zero or more eight-byte block descriptors, followed by the vendor unique parameters, if any. .pa Table 9-14 MODE SELECT Parameter List ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Reserved | -----|-----------------------------------------------------------------------| 1 | Reserved | -----|-----------------------------------------------------------------------| 2 |Reserved| Buffered Mode | Speed | -----|-----------------------------------------------------------------------| 3 | Block Descriptor Length | ============================================================================== | Block Descriptor(s) | ============================================================================== 0 | Density Code | -----|-----------------------------------------------------------------------| 1 | Number of Blocks (MSB) | -----|-----------------------------------------------------------------------| 2 | Number of Blocks | -----|-----------------------------------------------------------------------| 3 | Number of Blocks (LSB) | -----|-----------------------------------------------------------------------| 4 | Reserved | -----|-----------------------------------------------------------------------| 5 | Block Length (MSB) | -----|-----------------------------------------------------------------------| 6 | Block Length | -----|-----------------------------------------------------------------------| 7 | Block Length (LSB) | ============================================================================== | Vendor Unique Parameter(s) | ============================================================================== 0 _ n| Vendor Unique | | Parameter Byte(s) | ============================================================================== A buffered mode of zero indicates that the target shall not report a GOOD status on WRITE commands until the data blocks are actually written on the medium. A buffered mode of one indicates that the target may report a GOOD status on WRITE commands as soon as the data block has been transferred to the SCSI device buffer. One or more blocks may be buffered prior to writing the block(s) to the medium. Buffered modes of 2H through 7H are reserved. Code values for the speed field shall be assigned as follows: 0H Default (Use the peripheral device's default speed). 1H Use the peripheral device's lowest speed. 2H _ FH Use increasing peripheral device speeds. The block descriptor length specifies the length in bytes of all the block descriptors. It is equal to the number of block descriptors times eight and does not include the vendor unique parameters, if any. A block descriptor length of zero indicates that no block descriptors are included in the parameter list. This condition shall not be considered as an error. Each block descriptor specifies the medium characteristics for all or part of a logical unit. Each block descriptor contains a density code, a number of blocks, and a block length. Code values for the density code field are defined in Table 9-14.1. Table 9-14.1 Sequential-access Density Codes ============================================================================== Code Value Density ---------- ------------------------------------------------------------------ 00H Default (peripheral device's default or only density) Magnetic Tapes Width Density Reference mm. (Inch) Tracks BPMM (BPI) Code Type Standard Note ---------- ------ ------------ ---- ---- ------------ ---- 01H 12.7 (0.5) 9 32 (800) NRZI R X3.22-1983 3 02H 12.7 (0.5) 9 63 (1 600) PE R X3.39-1973 3 03H 12.7 (0.5) 9 246 (6 250) GCR R X3.54-1976 3 04H 6.3 (0.25) 4/9 315 (8 000) GCR C 2,4 05H 6.3 (0.25) 4/9 315 (8 000) GCR C X3.136-198X 2 06H 12.7 (0.5) 9 126 (3 200) PE R X3B5/85-98 1,3 07H 6.3 (0.25) 4 252 (6 400) IMFM C X3.116-198X 2 08H 3.81 (0.15) 4 315 (8 000) GCR CS X3B5/85-77 1,2 09H 12.7 (0.5) 18 C X3B5/85-76 1,3 0AH 12.7 (0.5) 22 267 (6 667) MFM C 2 0BH 6.3 (0.25) 4 63 (1 600) PE C X3.56-198X 2 0CH 12.7 (0.5) 24 500 (12 690) GCR C 2 0DH 12.7 (0.5) 24 999 (25 380) GCR C 2 80H _ FFH Vendor unique All others Reserved ============================================================================== Key: Code Type -------------------------------------------- ----------------------- NRZI Non Return to Zero, change on ones R Reel-to-Reel GCR Group Code Recording C Cartridge PE Phase Encoded CS Cassette IMFM Inverted Modified Frequency Modulation NOTES: (1) Working Draft. X3B5 assigns a new document number to each revision of their documents. Please contact the Chairman of X3B5 for the latest document number. (2) Serially Recorded. (3) Parallel Recorded. (4) Old format known as QIC-11. The number of blocks field specifies the number of logical blocks on the medium that meet the density code and block length in the block descriptor. A number of blocks of zero indicates that all of the remaining logical blocks of the logical unit shall have the medium characteristics specified by the block descriptor. The block length specifies the length in bytes of each logical block described by the block descriptor. A block length of zero indicates that the length shall be variable. .fo Section 9 132.1 .pa .fo Section 9 132.2 9.12 RESERVE UNIT and RELEASE UNIT Commands Peripheral Device Type: Sequential Access Operation Code Type: Optional Operation Code: 16H and 17H, respectively Table 9-15 RESERVE UNIT and RELEASE UNIT Commands ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code | -----|-----------------------------------------------------------------------| 1 | Logical Unit Number | 3rdPty | Third Party Device ID |Reserved| -----|-----------------------------------------------------------------------| 2 | Reserved | -----|-----------------------------------------------------------------------| 3 | Reserved | -----|-----------------------------------------------------------------------| 4 | Reserved | -----|-----------------------------------------------------------------------| 5 | Vendor Unique | Reserved | Flag | Link | ============================================================================== The RESERVE UNIT and RELEASE UNIT commands both use the command descriptor block shown in Table 9-15. 9.12.1 RESERVE UNIT Command. The RESERVE UNIT command (Table 9-15, operation code 16H) shall reserve the specified logical unit for the exclusive use by the requesting initiator or, if third-party reservation option is implemented, to another specified SCSI device. The reservation shall remain in effect until superceded by another RESERVE UNIT command from the initiator that made the reservation or until released by a RELEASE UNIT command from the same initiator, or a BUS DEVICE RESET message >From any initiator, or a "hard" RESET condition. The occurrence of the last two conditions is indicated by a sense key of UNIT ATTENTION on the next command following the condition. It is not an error to issue this command to a logical unit that is currently reserved to the requesting initiator. If the logical unit is previously reserved by another initiator, then the target shall either: (1) return a RESERVATION CONFLICT status (2) queue the reservation request and disconnect until all previously queued reservations have been released. When the logical unit is available, the target shall reconnect to perform the reservation If, after honoring the reservation, any other initiator then subsequently attempts to perform any command on the reserved logical unit other than a RESERVE UNIT command, which may be queued, or a RELEASE UNIT command, which shall be ignored, then the command shall be rejected with a RESERVATION CONFLICT status. .pn 133 .fo Section 9 # The third-party reservation option for the RESERVE UNIT command allows an initiator to reserve a logical unit for another SCSI device. This option is intended for use in multiple-initiator systems that use the COPY command. Any target that implements the third-party reservation option shall also implement the third-party release option (see 9.12.2). If the third-party (3rdPty) bit is zero, then the third-party reservation option is not requested. If the 3rdPty bit is one and the third-party reservation option is implemented, then the RESERVE UNIT command shall reserve the specified logical unit for the SCSI device specified in the third-party device ID field. The target shall preserve the reservation until superceded by another RESERVE UNIT command from the initiator that made the reservation or until released by the same initiator, by a BUS DEVICE RESET message from any initiator, or by a "hard" RESET condition. The target shall ignore (i.e., return GOOD status) any attempt made by any other initiator to release the reservation. If the 3rdPty bit is one and the third-party reservation option is not implemented, then the target shall reject the RESERVE UNIT command with a CHECK CONDITION status and a sense key of ILLEGAL REQUEST. An initiator that holds a current reservation may modify that reservation (e.g., switch third-parties) by issuing another RESERVE UNIT command to the same logical unit. The superceding RESERVE UNIT command shall release the previous reservation state only when the new reservation is granted. A superceding reservation takes priority over any previously queued reservation request. 9.12.2 RELEASE UNIT Command. The RELEASE UNIT command (Table 9-15, operation code 17H) shall release the logical unit if it is currently reserved by the requesting initiator. It is not an error to attempt to release a logical unit that is not currently reserved to the requesting initiator. However, it shall not be released if it is reserved by another initiator. The third-party release option for the RELEASE UNIT command allows an initiator to release a logical unit that was previously reserved using the third-party reservation option (see 9.12.1). This option shall be implemented if the third-party reservation option is implemented. This option is intended for use in multiple-initiator systems that use the COPY command. If the third-party (3rdPty) bit is zero, then the third-party release option is not requested. If the 3rdPty bit is one and the target implements the third-party release option, then the target shall release the specified logical unit, but only if the reservation was made using the third-party reservation option by the initiator that is requesting the release and for the same SCSI device as specified in the third-party device ID field. If the 3rdPty bit is one and the target does not implement the third-party release option, then the target shall terminate the command with a CHECK CONDITION status and the sense key shall be set to ILLEGAL REQUEST. .pa 9.13 ERASE Command Peripheral Device Type: Sequential Access Operation Code Type: Optional Operation Code: 19H Table 9-16 ERASE Command ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code | -----|-----------------------------------------------------------------------| 1 | Logical Unit Number | Reserved | Long | -----|-----------------------------------------------------------------------| 2 | Reserved | -----|-----------------------------------------------------------------------| 3 | Reserved | -----|-----------------------------------------------------------------------| 4 | Reserved | -----|-----------------------------------------------------------------------| 5 | Vendor Unique | Reserved | Flag | Link | ============================================================================== The ERASE command (Table 9-16) causes part or all of the remaining medium to be erased beginning from the current medium position. As used here, "erased" means either the medium shall be erased or a pattern shall be written on the medium that appears as gap to the target. The distance to be erased is controlled by the long bit. A long bit of one indicates that all remaining medium on the logical unit shall be erased. A long bit of zero indicates that a peripheral device specified portion of the medium shall be erased. Normally, short erases are used to create an extended gap for software controlled error recovery or for support of "update in place" functions. The medium position following an ERASE command with a long bit of one is not defined by this standard. NOTE: Some targets may reject ERASE commands with the long bit set to one if the medium is not positioned at the beginning-of-medium. .pa 9.14 MODE SENSE Command Peripheral Device Type: Sequential Access Operation Code Type: Optional Operation Code: 1AH Table 9-17 MODE SENSE Command ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code | -----|-----------------------------------------------------------------------| 1 | Logical Unit Number | Reserved | -----|-----------------------------------------------------------------------| 2 | Reserved | -----|-----------------------------------------------------------------------| 3 | Reserved | -----|-----------------------------------------------------------------------| 4 | Allocation Length | -----|-----------------------------------------------------------------------| 5 | Vendor Unique | Reserved | Flag | Link | ============================================================================== The MODE SENSE command (Table 9-17) provides a means for a target to report its medium, logical unit, or peripheral device parameters to the initiator. It is a complementary command to the MODE SELECT command (see 9.11) for support of a medium that may contain different densities, such as half-inch tapes. The allocation length specifies the number of bytes that the initiator has allocated for returned MODE SENSE data. An allocation length of zero indicates that no MODE SENSE data shall be transferred. This condition shall not be considered as an error. Any other value indicates the maximum number of bytes that shall be transferred. The target shall terminate the DATA IN phase when allocation length bytes have been transferred or when all available MODE SENSE data have been transferred to the initiator, whichever is less. The MODE SENSE data (Table 9-18) contains a four-byte header, followed by zero or more eight-byte block descriptors, followed by the vendor unique parameters, if any. .pa Table 9-18 MODE SENSE Data ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Sense Data Length | -----|-----------------------------------------------------------------------| 1 | Medium Type | -----|-----------------------------------------------------------------------| 2 | WP | Buffered Mode | Speed | -----|-----------------------------------------------------------------------| 3 | Block Descriptor Length | ============================================================================== | Block Descriptor(s) | ============================================================================== 0 | Density Code | -----|-----------------------------------------------------------------------| 1 | Number of Blocks (MSB) | -----|-----------------------------------------------------------------------| 2 | Number of Blocks | -----|-----------------------------------------------------------------------| 3 | Number of Blocks (LSB) | -----|-----------------------------------------------------------------------| 4 | Reserved | -----|-----------------------------------------------------------------------| 5 | Block Length (MSB) | -----|-----------------------------------------------------------------------| 6 | Block Length | -----|-----------------------------------------------------------------------| 7 | Block Length (LSB) | ============================================================================== | Vendor Unique Parameter(s) | ============================================================================== 0 _ n| Vendor Unique | | Parameter Byte(s) | ============================================================================== The sense data length specifies the length in bytes of the following mode sense data that is available to be transferred during the DATA IN phase. The sense data length does not include itself. Code values for the medium type field shall be assigned as follows: 00H Default (Only one medium type supported) 01H _ 7FH Reserved 80H _ FFH Vendor unique A write protected (WP) bit of zero indicates that the medium is write enabled. A write protected bit of one indicates that the medium is write protected. A buffered mode of zero indicates that the target does not report a GOOD status on WRITE commands until the data blocks are actually written on the medium. A buffered mode of one indicates that the target may report a GOOD status on WRITE commands as soon as the data block has been transferred to the SCSI device buffer. One or more blocks may be buffered prior to writing the block(s) to the medium. Buffered modes of 2H through 7H are reserved. Code values for the speed field shall be assigned as follows: 0H Default (only one speed supported) 1H Lowest peripheral device speed 2H _ FH Increasing peripheral device speeds The block descriptor length specifies the length in bytes of all the block descriptors. It is equal to the number of block descriptors times eight and does not include the vendor unique parameters, if any. A block descriptor length of zero indicates that no block descriptors shall be included in the parameter list. This condition shall not be considered as an error. Each block descriptor specifies the medium characteristics for all or part of a logical unit. Each block descriptor contains a density code, a number of blocks, and a block length. Code values for the density code field are defined in Table 9-14.1. The number of blocks field specifies the number of logical blocks on the medium that meet the density code and block length in the block descriptor. A number of blocks of zero indicates that all of the remaining logical blocks of the logical unit have the medium characteristics specified by the block descriptor. The block length specifies the length in bytes of each logical block described by the block descriptor. A block length of zero indicates that the length is variable. .pa 9.15 LOAD/UNLOAD Command Peripheral Device Type: Sequential Access Operation Code Type: Optional Operation Code: 1BH Table 9-19 LOAD/UNLOAD Command ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code | -----|-----------------------------------------------------------------------| 1 | Logical Unit Number | Reserved | Immed | -----|-----------------------------------------------------------------------| 2 | Reserved | -----|-----------------------------------------------------------------------| 3 | Reserved | -----|-----------------------------------------------------------------------| 4 | Reserved | Re-Ten | Load | -----|-----------------------------------------------------------------------| 5 | Vendor Unique | Reserved | Flag | Link | ============================================================================== The LOAD/UNLOAD command (Table 9-19) requests that the target enable or disable the logical unit for further operations. This command may also be used to request the re-tension function on peripheral devices that support this function. A load bit of one indicates that the medium on the logical unit shall be loaded and positioned to the beginning-of-medium or load-point as determined by the peripheral device. A load bit of zero indicates that the medium on the logical unit shall be positioned for removal from the peripheral device. Status shall be returned after the medium is positioned unless the immediate (Immed) bit is one. If the Immed bit is one, status may be returned as soon as the command has been accepted. A re-tension (Re-Ten) bit of one indicates that the medium on the addressed logical unit shall be correctly tensioned before the LOAD/UNLOAD command is completed. This is an optional function intended for use by those peripheral devices that support the re-tension function. .pa 9.16 PREVENT/ALLOW MEDIUM REMOVAL Command Peripheral Device Type: Sequential Access Operation Code Type: Optional Operation Code: 1EH Table 9-20 PREVENT/ALLOW MEDIUM REMOVAL Command ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code | -----|-----------------------------------------------------------------------| 1 | Logical Unit Number | Reserved | -----|-----------------------------------------------------------------------| 2 | Reserved | -----|-----------------------------------------------------------------------| 3 | Reserved | -----|-----------------------------------------------------------------------| 4 | Reserved | Prevent| -----|-----------------------------------------------------------------------| 5 | Vendor Unique | Reserved | Flag | Link | ============================================================================== The PREVENT/ALLOW MEDIUM REMOVAL command (Table 9-20) requests that the target enable or disable the removal of the medium in the logical unit. A prevent bit of one shall inhibit mechanisms that normally allow removal of the medium. A prevent bit of zero shall allow removal of the medium. This prevention of medium removal condition shall terminate upon receipt of a PREVENT/ALLOW MEDIUM REMOVAL command with the prevent bit set to zero, or by the receipt of a BUS DEVICE RESET message from any initiator or by a "hard" RESET condition. .pa