PEF2091 Siemens Semiconductor Group, PEF2091 Datasheet - Page 158

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

PEB 2091
PEF 2091
Operational Description
Line Active
In the "Line Active" state, the IEC-Q transmits transparently in both directions. The
U-Interface is synchronized and the maintenance channel is operational. The IEC-Q
stays in the line-active state
– during a normal activation procedure while the "ACT" bit = (0) is received
– when an analog loop-back is established
– while C/I-command AR0 is applied downstream
In the case of normal activation with call control, binary "0s" have to be applied to the B
and D channels in downstream direction. After the C/I-channel indication UAI has been
issued, the layer-2 receiver should be fully operational to prevent the first layer-2
message issued by the NT side upon the receipt of the ALI-code in the TE, to be lost.
Loss of Signal
The "Loss of Signal" state is entered upon the detection of a failure condition i.e. loss of
receive signal (LSUE). The ACT bit is set to "0" and the C/I-channel indication LSL is
issued. The IEC-Q waits for the C/I-channel command RES1 to enter the "Receive
Reset" state.
Loss of Synchronization
The "Loss of Synchronization" state is entered upon the detection of a failure condition
i.e. loss of framing by the LT Receiver (LOF). The ACT-bit is set to "0" and the
C/I-channel indication RSY is issued. The IEC-Q waits for the C/I-channel command
RES1 to enter the "Tear Down Error" state and subsequently the "Receive Reset" state.
Pending Deactivation
"Pending Deactivation" is a transient state entered after the receipt of a DR-code. The
DEA-bit is set to "0". Timer T10 assures that the DEA-bit is set to "0" in at least three
consecutive superframes before the transmit level is turned off.
Pending Transparent
"Pending Transparent" is a transient state entered upon the detection of ACT = 1 and left
by T8. The ACT-bit is set to "1". The purpose of this state is to issue the C/I-channel
indication AI (corresponding to "ready for sending") 24 ms after the ACT-bit has been set
to "1" by the LT-transceiver. This assures that under normal operating conditions the
AI-indication is issued first on the TE side and only afterwards on the LT side. Thus the
layer-2 receiver in the TE is already operational when the first layer-2 message is issued
by the LT side.
Semiconductor Group
158
Data Sheet 01.99