DS34S132 DATA SHEET
19-4750; Rev 1; 07/11
42 of 194
Table 9-5. CAS Translation using RDAT and TDAT
TXP Direction
RXP Direction
SCTXDFSE to
PRCR1.MFS
TDM Port RDAT
TXP Packet Out
RXP Packet In
TDM Port TDAT
PTCR1.MFS
Format
Frm 1-12
Frm 13-24
Frm 1-12
Frm 13-24
Format
ESF to SF A1B1C1D1
A1B1A1B1
A1B1
SF
SF to ESF A1B1
A2B2
A1B1CD
ESF
SF to SF
A1B1
A2B2
A1B1A2B2
A1B1
A2B2
SF
ESF to ESF A1B1C1D1
A1B1C1D1
ESF
E1 to E1
A1B1C1D1
E1
Special considerations:
Each system should be analyzed to determine whether the 2-bit to 4-bit translation function is appropriate. The
method of appending a fixed, programmed “CD” value in one direction (SF to ESF) and discarding the “CD” bits in
the other direction (ESF to SF) may not be valid.
In applications where T1-SF CAS Signaling is carried in RXP packets, because the S132 stores 24 frames of T1-
SF CAS Signaling, it is possible (during a loss of RXP packet condition) that a constantly alternating 2-bit CAS code
(A1B1 ≠ A2B2) is transmitted at the TDM Port if the last 2 received AB CAS-codes are 2 different values, the Jitter
Buffer underruns (e.g. RXP packet fault) and the CAS “Last Value” function is enabled (B.BCDR1.SCRXBCSS).
This can occur, for example, if the far end of the PW transmitted an On-hook to Off-hook CAS Code transition in the
last received RXP packet. If this condition occurs (A1B1 ≠ A2B2), the TDM Port transmitted CAS codes will alternate
between these two values every 12 frames. Each system should be evaluated to determine whether this condition
is acceptable (an external T1 Framer with CAS debounce function should filter out the alternating pattern).
The support of CAS Signaling in a system that allows the use of multiple Nx64 PWs with a single T1/E1 may
require the system to be compliant with the defect and alarm requirements of a Digital Cross-Connect. When a
T1/E1 is divided into multiple segment/paths, the segments are unable to use the T1/E1 framing as an indication of
the state of the connection. For example if 2 PWs are merged into a single T1/E1, a far end T1/E1 fault in the RXP
direction of PW #1 (e.g. LOS) cannot be directly communicated over the local, T1/E1 transmit port since that would
imply that PW #2 is experiencing the same fault (i.e. the local T1/E1 transmit Port cannot forward the T1/E1-AIS,
Alarm Indication Signal, for PW #1 without indicating the same for PW #2; some systems allow DS0-AIS). Each
system should be analyzed to determine whether Digital Cross-Connect defect and alarm conditioning is required.
If these functions are required, they should be implemented external to the S132 (e.g. in the T1/E1 Framer).
9.2.4.2 TSA Block Loopbacks
The TSA Timeslots can be programmed to loopback data using a Bundle Loopback, TDM Port Line Loopback or
TDM Port Timeslot Loopback (see
Figure 9-13). Any number of Timeslots, Bundles and/or TDM Ports can be in
Loopback at the same time.
The Bundle Loopback sends packet payload data that has been received for an RXP Bundle back toward the
Ethernet Port in TXP packets for the same Bundle. When the Bundle Loopback is enabled (Pn.PTCR3.RXTXTSL),
the RXP packet payload data is processed as though it will be transmitted at a TDM Port. But when the payload
data reaches the TSA block the data is looped back in the TXP direction and processed as though the data was
received from the TDM port. To work properly all Timeslots associated with the Bundle should be programmed into
the Bundle Loopback state.
The TDM Port Line Loopback and TDM Port Timeslot Loopback send payload data from the receive TDM Port back
toward the transmit TDM Port without any packet processing functions. The TDM Port Timeslot Loopback
(Pn.PTCR3.PRPTTSL) allows loopback selection on a per-Timeslot basis while the TDM Port Line Loopback
(Pn.PTCR2.PRPTLL) provides a loopback of all Receive TDM Port Data.
9.2.5 TDM Port Data Processing Engines
A TDM Port is assigned to a Bundle using B.BCDR4.PNS. The format of the TDM Port data streams can be
Unstructured, Structured T1/E1 without CAS or Structured T1/E1 with CAS and are processed using 3 engine
types: HDLC, SAT/CES and Clock Recovery. The combination of B.BCDR1.PMT (Payload Engine Type),
B.BCDR3.TXBTS (TXP Bundle Structure), B.BCDR4.RXBTS (RXP Bundle Structure) and B.BCDR4.PCRE (Clock
Recovery Enable) select the payload format and engine type for each Bundle. Enabling a particular Engine Type for