
DS34S132 DATA SHEET
19-4750; Rev 1; 07/11
41 of 194
ESF formats. For the T1 SF format this means that two successive 2-bit CAS Codes from 2 consecutive SF frames
are stored.
For T1 ESF and E1, the 4-bit ABCD CAS-codes received at a T1/E1 Port are stored and forwarded unmodified.
When the T1 SF format is used the S132 “extends” the T1-SF, 2-bit AB CAS-codes into a 4-bit CAS field since the
PW Sub-channel CAS Signaling requires a 4-bit field (regardless of whether it is T1-ESF, T1-SF or E1). Two
dummy bits are appended to and removed from the T1-SF, AB CAS-code to fill the packet’s 4-bit CAS field.
Most applications will use the same T1/E1 framing on both ends of the PW (e.g. T1-ESF to T1-ESF). For T1
applications, the S132 can be programmed to provide a translation between the 2-bit SF CAS Codes and 4-bit ESF
CAS Codes. This is a unidirectional function that can be enabled in the TXP direction (see
Figure 9-12, “ESF to SF
Translation Example”). When translating 4-bit, ESF, “ABCD” CAS into 2-bit, SF, “AB” CAS the “CD” bits are
discarded. When translating 2-bit, SF, “AB” CAS into 4-bit, ESF, “ABCD” CAS the S132 generates an ABCD code
by appending a programmed, 2-bit “CD” value to the received, 2-bit “AB” code (the “CD” insertion bits are
programmed using Pn.PRCR1.CBVSE and Pn.PRCR1.DBVSE).
Table 9-4 describes how to program each of the various translation functions and how the 4-bit fields are
interpreted when using RSIG and TSIG. The table should be read from left to right. The “TXP Direction”,
“SCTXDFSE & PRCR1.MFS Format” column identifies each programmed translation function (e.g. ESF to SF). For
example, for “ESF to SF”, Pn.PRCR1.FFS and Pn.PRCR1.MFS are programmed for ESF; B.BCDR1.SCTXDFSE is
programmed for SF; Pn.PTCR1.FFS and Pn.PTCR1.MFS are programmed for SF.
The RSIG column includes two sub-columns that provide an example of CAS data that might be received in frames
1 - 24. The “TXP Packet Out” columns indicate how the CAS codes received from the RSIG pin would be
transmitted in the TXP Packets. The “RXP Packet In” column is identical to the “TXP Packet Out” column to
represent the process on the opposite end of the PW (as though the TXP Out is connected to the RXP In). The
TSIG column indicates how the CAS code (received from the RXP Packet) would be transmitted on the TSIG pin.
The “Format” settings determine whether CAS is sent once every 12 T1 frames or once every 24 T1 frames.
SCTXDFSE specifies the RSIG frame rate. PRCR1.MFS specifies the “TXP Packet Out” frame rate. PTCR1.MFS
specifies the TSIG frame rate.
The protocols for the RSIG and TSIG pins always include a 4-bit field for the CAS Code (even for the SF format). In
the SF format only 2-bits of the 4-bit field are regarded as valid by the protocol. In the “RSIG” column, “XY” is used
to indicate that the values of the two “extra” bits are unknown. An external T1 SF Framer will ignore the last two
TSIG dummy bits. The “SF to SF”, “ESF to ESF” and “E1 to E1” translation functions are included in the table to
show how the CAS codes are handled for all combinations.
Table 9-4. CAS Translation using RSIG and TSIG
TXP Direction
RXP Direction
SCTXDFSE to
PRCR1.MFS
TDM Port RSIG
TXP Packet Out
RXP Packet In
TDM Port TSIG
PTCR1.MFS
Format
Frm 1-12
Frm 13-24
Frm 1-24
Frm 1-12
Frm 13-24
Format
ESF to SF A1B1C1D1
A1B1A1B1
A1B1A1B1 A1B1A1B1
SF
SF to ESF A1B1X1Y1 A2B2X2Y2 A1B1CD
A1B1CD
ESF
SF to SF
A1B1X1Y1 A2B2X2Y2 A1B1A2B2
A1B1A2B2
A1B1A1B1 A2B2A2B2
SF
ESF to ESF A1B1C1D1
A1B1C1D1
ESF
E1 to E1
A1B1C1D1
E1
Notes: The “X” and “Y” values mean ”any value”, these values doesn’t matter since these bit positions are ignored.”
Table 9-5 describes the same information for applications that use RDAT and TDAT instead of RSIG and TSIG. For T1-SF, TDAT and RDAT only exchange a 2-bit CAS field for each 12- frame, SF multi-frame.