PEF2091 Siemens Semiconductor Group, PEF2091 Datasheet - Page 166

• Manufacturer Part Number: PEF2091
• Description: ICs for Communications(ISDN Echocancellation Circuit)
• Manufacturer: Siemens Semiconductor Group

Semiconductor Group
LSU
LSUE
SFD
FD
TL
BBD0/1
Loss of Signal level on the U-interface
This signal indicates that a loss of signal level for a duration of 3 ms has
been detected on the U-interface. This short response time is relevant in all
cases where the NT waits for a response (no signal level) from the LT side,
i.e. after a deactivation has been announced (receipt of DEA = 0), after the
NT has lost framing, and after timer T1 has elapsed.
Loss of Signal level on the U-interface (error condition)
After a loss of signal has been noticed, a 588 ms timer is started. When it
has elapsed, the LSUE-criterion is fulfilled. This long response time (see
also LSU) is valid in all cases where the NT is not prepared to lose signal
level i.e. the LT has stopped transmission because of loss of framing, an
unsuccessful activation, or the transmission line is interrupted.
Note that 588 ms represent a minimum value; the actual loss of signal might
have occurred earlier, e.g. when a long loop is cut at the NT side and the
echo coefficients need to be readjusted to the new parameters. Only after
the adjusted coefficients cancel the echo completely, the loss of signal is
detected and the timer can be started (if the long loop is cut at the remote
end, the coefficients are still correct and loss of signal will be detected
immediately).
Superframe (ISW) Detected on U-interface
Frame (SW) Detected on U-interface
Wake-up signal received from the LT
The IEC-Q is requested to start an activation procedure. The TL-criterion is
fulfilled when 12 consecutive periods of the 10-kHz wake-up tone were
detected.
When in the "Pending Timing" state and automatic activation after reset is
selected (NT-Auto Activation mode), a recognition of TL is assumed every
time the "Pending Timing" state has been entered from the "Test" state
(caused by C/I code DI). This behavior allows the IEC-Q to initiate activation
attempts after having been reset (see "Activation Attempt Initiated by NT in
NT-Auto Activation Mode", page 142).
Binary "0s" or "1s" detected in the B- and D-channels
This internal signal indicates that for 6-12 ms, a continuous stream of binary
"0s" or "1s" has been detected. It is used as a criterion that the Receiver has
acquired frame synchronization and both its EC- and EQ-coefficients have
converged. BBD0 corresponds to the signal SL2 in the case of normal
activation and BBD1 corresponds to the internally received signal SN3 in
case of an analog loop back in the NT mode.
166
Operational Description
Data Sheet 01.99
PEB 2091
PEF 2091