During start\(hyup, the network shall produce symbols at the nominal line
rate within the tolerance specified in \(sc\ II.2.1.2.
.PP
The symbol rate from the NT1 shall be 80\ kbauds \(+- | 00\ ppm.
.bp
.RT
.LP
.rs
.sp 31P
.ad r
\fBFigure II\(hy7/G.961 [T17.961] \ \
(\*`a traiter comme tableau MEP), p.12\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
.sp 3
II.10.1.3\ \ \fIStart\(hyup sequence\fR
.sp 9p
.RT
.PP
Figure II\(hy6/G.961 shows the sequence of signals at the interface
that are generated by the transceivers. The transition points in the sequence
are also defined in Figure\ II\(hy7/G.961. For further information on the
events at the interface at reference point\ T, the reader is referred to
Recommendation\ I.430.
.RT
.sp 1P
.LP
II.10.1.4\ \ \fR \fIWake\(hyup\fR
.sp 9p
.RT
.PP
When transceivers meeting the optional warm\(hystart activation\(hytime
requirements, or when cold\(hystart\(hyonly NT1s having the optional capability
of
initiating start\(hyup, are in the RESET state or are deactive as a result of
responding to a deactivation request, either transceiver may initiate start\(hyup
by sending a tone as defined in Figure\ II\(hy7/G.961.
.bp
.RT
.sp 2P
.LP
II.10.1.5\ \ \fIProgress indicators\fR
.sp 1P
.RT
.sp 1P
.LP
II.10.1.5.1\ \ \fIActivation\fR
.sp 9p
.RT
.PP
In the NT1 to LT direction, the act bit remains set to ZERO until the customer
equipment indicates progress in getting ready to transmit. The
corresponding action at the T\ reference point in the customer equipment is
receipt of the signal INFO3. To communicate this progress indication, act
from the NT1 is set to ONE. Assuming INFO3 occurs before T6 and T7, this
progress
indication shall not affect overhead symbols at the interface until T6, when
the NT1 overhead bits are allowed to be normal, and may not be detected
by the LT until T7.
.PP
After event T7 (Figure\ II\(hy6/G.961) and after act = ONE is received
from the NT1, the LT sets the act bit to ONE to communicate readiness for
layer\ 2 communication (see \(sc\ II.8.3.2.2).
.RT
.sp 1P
.LP
II.10.1.5.2\ \ \fIDeactivation\fR
.sp 9p
.RT
.PP
Transceivers in the active state that meet optional warm\(hy start
activation\(hytime requirements shall cease transmission on the basis of
the DEA bit (see \(sc\ II.8.3.2.3) and subsequent loss of received signal.
The DEA bit from the LT shall be set to ONE before activation is initiated.
The LT shall
announce deactivation by setting DEA to ZERO.
.PP
The LT shall send DEA = ZERO in at least three multiframes before
ceasing transmission. It shall cease transmission before sending a DEA
bit in the multiframe following the multiframe in which DEA\ =\ ZERO is
sent the last
time. During the multiframes with DEA\ =\ ZERO the NT1 has time to prepare for
deactivation. The NT1 shall, upon the detection of loss of signal from
the LT, cease transmission, enter the receive reset state and deactivate.
Its response time to a loss of received signal shall be such that the NT1
will enter the
.PP
receive reset state within 40\ ms. of the occurrence of the transition to no
signal at its interface. As specified in the definitions given at the beginning
of \(scII\(hy10, it shall not initiate the transmission of wake\(hyup tone
for a period of at least 40\ ms. after it ceases transmission and then
it shall enter the
full reset state. The LT shall enter the full reset state upon the detection
of the loss of received signal.
.PP
LT transceivers not implementing optional warm\(hystart activation\(hytime
requirements shall continuously set DEA to ONE.
.RT
.sp 1P
.LP
II.10.2\ \ \fITimers\fR
.sp 9p
.RT
.PP
Timers shall be used to determine entry into the reset states. Upon the
occurrence of any of the following conditions:
.RT
.LP
1)
failure to complete start\(hyup within 15 s. (warm or cold
start),
.LP
2)
loss of received signal for more than 480\ ms., or
.LP
3)
loss of synchronization for more than 480 ms.,
.LP
a transceiver shall respond as follows: Upon satisfying
conditions\ 1) or\ 3), it shall cease transmission and then, upon the subsequent
detection of the loss of received signal, the transceiver shall enter the
receive reset state. Its response time to a loss of signal (after conditions\
1) or\ 2) have been satisfied) shall be such that it shall enter the receive
reset state and be capable of responding to the initiation of wake\(hyup
tone by the
far\(hyend transceiver within 40\ ms. after the far end transceiver ceases
transmission. Upon satisfying condition\ 2), the transceiver shall immediately
enter the receive reset state. As specified in part\ 7) of \(sc\ II.10,
a
transceiver shall remain in the receive reset state for at least 40\ ms.,
after which it shall enter the full reset state. The transciever may not
initiate transmission of wake\(hyup tone in the receive reset state.
.PP
For conditions 2) and 3), the requirements apply to transceivers after
start up, i.e., after multiframe synchronization is achieved (see T6 and
T7 in Figure\ II\(hy6/G.961 for NT1 and LT transceivers, respectively).
.PP
In addition, an NT1 shall enter the full reset state if signal is not received
within 480\ ms. after it ceases the transmission of TN, or SN1 if it is
sent (see T2 to T3 in Figures\ II\(hy6/G.961 and\ \ II\(hy7/G.961).
.bp
.RT
.sp 2P
.LP
II.10.3\ \ \fIDescription of the activation procedure\fR
.sp 1P
.RT
.sp 1P
.LP
II.10.3.1\ \ \fIActivation from customer equipment\fR
.sp 9p
.RT
.PP
While the NT1 and LT remain in the deactive state as a result of
receiving and responding to a deactivation request, or while they are in
RESET, a request for activation from the customer equipment shall result
in the TN
signal (tone) being sent from the NT1 toward the LT. The LT, on receiving TN
shall remain silent until detection of cessation of signal from the NT1. The
rest of the sequence then follows as indicated in Figures\ II\(hy6/G.961
and\ II\(hy7/G.961. If the LT happens to try to activate at the same time
it may
send a TL tone during the TN tone without harm.
.PP
While in the reset state, NT1 may initiate transmission only to
request service. Under all other conditions where the system has been
deactivated, the NT1 shall remain quiet, i.e., they shall not start
transmitting any signal until the NT1 has received the TL signal from
the LT.
.RT
.sp 1P
.LP
II.10.3.2\ \ \fIActivation from the network\fR
.sp 9p
.RT
.PP
While the NT1 and LT remain in the deactive state as a result of
receiving and responding to a deactivation request, or while they are in
RESET, a request for activation from the LT shall result in the TL signal
being sent from the LT toward the NT1. The NT1, on receiving TL shall respond
with TN
within 4\ ms from the beginning of TL. The rest of the sequence then
follows as indicated in Figures\ II\(hy6/G.961 and II\(hy7/G.961.
.RT
.sp 1P
.LP
II.10.3.3\ \ \fISequence charts\fR
.sp 9p
.RT
.PP
Examples of sequence charts for activation by both terminal and ET equipment
are given in Figures\ II\(hy8/G.961 and\ II\(hy9/G.961.
.RT
.LP
.rs
.sp 23P
.ad r
\fBFigure II\(hy8/G.961, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 23P
.ad r
\fBFigure II\(hy9/G.961, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
II.10.3.4\ \ \fITransparency\fR
.sp 9p
.RT
.PP
Transparency of the transmission in both directions by the NT1
shall be provided after the NT achieves full operational status (T6), and
both act\ =\ ONE form the LT and DEA\ =\ ONE. Full operational status of
the NT1 means that the NT1 has:
.RT
.LP
1)
acquired bit timing and frame synchronization from the
incoming signal from the LT,
.LP
2)
recognized the multiframe marker from the LT,
.LP
3)
fully converged both its echo canceler and equalizer
coefficients.
.PP
Transparency of the transmission in both directions at the LT
shall be provided when the LT:
.sp 9p
.RT
.LP
1)
achieves full operational status (T7),
.LP
2)
detects the presence of the multiframe marker from the NT1,
.LP
3)
receives act = ONE from the NT1.
.PP
Full operational status at the LT means that the LT has:
.sp 9p
.RT
.LP
1)
acquired bit timing phase of the incoming signal from the
NT1, and frame synchronization,
.LP
2)
recognized the multiframe marker from the NT1,
.LP
3)
fully converged both its echo canceler and equalizer
coefficients.
.PP
After both the LT and the NT1 achieve transparency in both
directions, the act bits shall continue to reflect the state of readiness of
the LT and the terminal equipment for layer\ 2 communication. The act bit
in the LT\(hyto\(hyNT1 direction shall reflect the status of the LT side
of the interface. The act bit in the NT1\(hyto\(hyLT direction shall reflect
the status of the NT1 side of the interface. Whenever either end, for any
reason, loses its readiness to communicate at layer\ 2 (e.g., the terminal
is unplugged), that end shall set
its transmitted act bit to ZERO. A change of status of this bit shall be
repeated in at least three consecutive transmitted multiframes.
.bp
.sp 1P
.LP
II.10.4\ \ \fIState transition table for the NT1\fR
.sp 9p
.RT
.PP
Table II\(hy3/G.961 provides an example of a state transition table
for the NT1 as a function of INFOs, SIGs, and Timers.
.RT
.ce
\fBH.T. [T12.961]\fR
.ce
TABLE\ II\(hy3/G.961
.ce
\fBState transition table for the NT1 as a function of INFOs, SIGs\fR
.ce
.ce
\fBand timers\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(24p) | cw(30p) | cw(12p) | cw(12p) | cw(12p) | cw(12p) | cw(12p) | cw(18p) | cw(12p) | cw(18p) | cw(12p) | cw(18p) | cw(12p) | cw(12p) | cw(12p) , ^ | ^ | c | c | c | c | c | c | c | c | c | c | c | c | c
^ | ^ | c | c | c | c | c | c | c | c | c | c | c | c | c.
Event {
State name
State code
Tx
(Note 6)
} Power off Full reset Alerting EC training EC cnvrg'd FW sync. IFW sync. Pending active Active Pending deact'n Tear down TE inactive Rcv. reset
NT0 NT1 (T0) NT2 NT3 (T1) NT4 (T2) NT5 (T5) NT6 (T6) NT7 NT8 NT9 NT10 NT11 NT12 SN0 INFO 0 SN0 INFO 0 TN INFO 0 SN1 INFO 0 SN0 INFO 0 SN2 INFO 0 SN3 ACT=0 INFO 2 SN3 ACT=1 INFO 2 SN3 ACT=1 INFO 4 SN3 (Note 7) SN0 INFO 0 SN3 ACT=0 INFO 2 SN0 INFO 0
\ \(em\ For symbols and abbreviations, see Table II\(hy4/G.961.
.nr PS 9
.RT
.ad r
\fBTable II\(hy3/G.961 [T12.961], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
II.10.5\ \ \fIState transition table for the LT\fR
.sp 9p
.RT
.PP
Table II\(hy4/G.961 provides an example of a state transition table
for the LT as a function of FEs, SIGs, and Timers.
.RT
.ce
\fBH.T. [T13.961]\fR
.ce
TABLE\ II\(hy4/G.732
.ce
\fBState transition table for the LT as a function of FEs, SIGs\fR
.ce
.ce
\fBand timers\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(24p) | cw(30p) | cw(12p) | cw(12p) | cw(12p) | cw(12p) | cw(12p) | cw(18p) | cw(12p) | cw(18p) | cw(12p) | cw(18p) | cw(12p) | cw(12p) | cw(12p) , ^ | ^ | c | c | c | c | c | c | c | c | c | c | c | c | c
^ | ^ | c | c | c | c | c | c | c | c | c | c | c | c | c.
Event State name State code Tx Power off Full reset Alerting Awake EC training EC cnvrg'd FW sync. IFW sync. Active Deact'n alert Tear down Pending deact'n Rev. reset
Name Deactivation Pending activation step 1 Pending activation step 2 Pending activation step 3 Pending activation step 4 Line only active Pending activation T int. T interf + line active Lost of frame at U in NT6 Lost of frame at U in NT8, 9 Pending deactivat. exp. TA Pending deactivat. IU6 (DR) U inter. active loop 2 Loop 2 active Loss of fr. at U loop 2
_
.T&
lw(66p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) | cw(18p) , ^ | c | c | c | c | c | c | c | c | c | c | c | c | c | c | c.
{
\ \ \ \ \ \
Signals \ \ \ \ \ \
Line
\ \ \ \ \
\ \ \ \ \ Tx \ \ \ \ \ \
INFO
New \ \ \ \ \ \ \ \ \ \ \ \
S/T
event Rx
} IU0 IU11 asy IU11 IU21 IU3 IU5 + UAI on CL IU5 + X on CL IU5 + AI on CL IU0 IU0 IU0 IU5 + X on CL IU5 + UAI or RSY IU5 + AI on CL IU0
INFO 0 INFO 0 INFO 0 INFO 0 INFO 0 INFO 0 INFO 2 INFO 4 INFO 0 INFO X INFO 0 INFO 0 INFO 2 INFO 4 INFO X
Name Deactivation Wait activation Pending activat. step 1 Pending activat. step 2 Pending activat. step 3 Pending activat. step 4 Line only active T int. or loop\ 2 active Loss of frame at U in LT8 Loss of frame at U in LT7 Remote error indication Loss of frame at U in LT11 Pending deactivation
_
.T&
lw(66p) | cw(18p) | cw(24p) | cw(18p) | cw(24p) | cw(18p) | cw(24p) | cw(18p) | cw(24p) | cw(18p) | cw(24p) | cw(18p) | cw(24p) | cw(18p) , ^ | c | c | c | c | c | c | c | c | c | c | c | c | c.
{
\ \ \ \ \ \
Signals \ \ \ \ \ \
Line
\ \ \ \ \
\ \ \ \ \ Tx \ \ \ \ \ \
INFO
New \ \ \ \ \ \ \ \ \ \ \ \
V
1
event Rx
} IU0 IU0 IU12 IU22 IU4 IU6 + FE on CL IU6 + FE on CL IU6 + FE on CL IU6 + FE on CL IU6 + FE on CL IU6 + FE on CL IU6 + FE on CL IU6 + FE on CL
FE 6 (DI) FE 2 (AR) FE 2 (AR) FE 2 (AR) FE 2 (AR) FE 2 (AR) FE 3 (UAI) FE 4 (AI) FE 7 (RSY) FE 7 (RSY) FE 7 (RSY) FE 7 (RSY) FE receiv. from CL