PEF2091 Siemens Semiconductor Group, PEF2091 Datasheet - Page 152

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

Semiconductor Group
CRCOK
LOF
LSEC
LSU
LSUE
SEC
SFD
– ACT = 0 indicates the loss of transparency on the NT side (loss of framing
Cyclic Redundancy Check OK
This input is used as a criterion that the Receiver has acquired frame
synchronization and both its EC and EQ coefficients have converged.
Loss of Framing on the U-interface
This condition is fulfilled if framing is lost for 576 ms. 576 ms are the upper
limit. If the correlation between synchronization word and input signal is not
optimal, LOF can be issued earlier.
Loss of Signal Level behind the Echo Canceler
In the "Awake" state, this input is used as indication that the NT has ceased
the transmission of signal SN1. In the EC-training state, this input is used as
an internal signal indicating that the EC in the LT has converged.
Loss of Signal Level on the U-interface
This signal indicates that a loss of signal level for the duration of 3 ms has
been detected on the U-interface. This short response time is relevant in all
cases where the LT waits for a response (no signal level) from the NT side,
i.e. after a deactivation procedure has been started or after loss of framing
in the LT occurred.
Loss of Signal Level on the U-interface (error condition)
After a loss of signal level has been noticed, a 492 ms timer is started. After
this timer has elapsed, the LSUE-criterion is fulfilled. This long response
time (see also LSU) is valid in all cases where the LT is not prepared to lose
signal level. Note that 492 ms represent a minimum value; the actual loss of
signal might have occurred earlier, e.g. when a long loop is cut at the LT
side, the echo coefficients need to be readjusted to new parameters. Only
after the adjusted coefficient 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 a loss of signal will be detected
immediately).
Signal Level behind the echo canceler
This signal indicates that a signal level corresponding to SN2 from the NT
has been detected on the U-interface.
Superframe Detected
indication UAI is issued. Until the status "ready for sending" is reached,
binary "0s" have to be passed in the B- and D-channels on DIN.
or loss of signal level on the S/T-interface). The IEC-Q informs the LT
side by issuing the C/I-channel indication EI2, but performs no state
change or other actions.
152
Operational Description
Data Sheet 01.99
PEB 2091
PEF 2091