PXB4219 Datasheet, PDF (57/290 Pages) Infineon Technologies AG – IWE8 Interworking Element for 8 E1/T1 Lines

PXB4219 / PXB4220 / PXB4221
Operational Description
4.3.1.4 Transport of CAS Information
The four CAS bits for each time slot are transported within one multiframe from the
framer to the IWE8. A signalling buffer in the internal RAM (256 x 4 x 2bit) holds the CAS
bits from the framer interface. The activation of CAS packetization can be done via
“p_cas” in the register “pcfN”.
The CAS bits will be packed in a signalling substructure after the payload of one
multiframe has been packetized.
4.3.1.5 CAS Conditioning and Freezing Upstream
Normally the framer device is responsible for signalling freezing or signalling
conditioning in case of line failure. If the framer doesn’t support the feature the IWE8 can
also fulfill the requirements according to Bellcore TR-NWT-000170 [14].
Pin “FRLOS = 1" indicates that the CAS information from the framer device is invalid and
CAS conditioning or freezing upstream is starting. This state remains active until valid
CAS bits are available indicated by “FRLOS = 0".
CAS freezing means that the last valid CAS information is repeated as long as the error
cause exists. In case of CAS conditioning for each timeslot individual CAS conditioning
nibbles are sent instead. Selection between both procedures is done by setting
“sig_cond” in the “AAL Receive Reference Slot”. If the channel bandwidth is one slot, the
signalling conditioning nibbles are defined in the field “next_slot_nr” of the “AAL Receive
Reference Slot”. If the channel bandwidth is more than one slot, the signalling
conditioning nibbles are defined in the “sig_cond_nibble” of the “AAL Receive
Continuation Slot”. In the latter case the signalling conditioning nibbles defined in the first
“AAL Receive Continuation Slot” are used for the first two slots.
Table 15 Definition of the CAS Signalling Conditioning Nibbles.
Slot Number Channel Bandwidth = 1 Slot Channel Bandwidth >= 2 Slots
1
“next_slot_nr” of the “AAL
“sig_cond_nibble” of the first “AAL
Receive Reference Slot”
Receive Continuation Slot”
2
-
“sig_cond_nibble” of the first “AAL
Receive Continuation Slot”
3
-
“sig_cond_nibble” of the second
“AAL Receive Continuation Slot”
N
-
“sig_cond_nibble” of the N-1th
“AAL Receive Continuation Slot”
Data Sheet
57
2002-05-06