DS34S132 DATA SHEET
19-4750; Rev 1; 07/11
34 of 194
of the Sequence Number. Both Timestamp types provide a measure of time, one referenced to a common clock,
the other referenced to the receive TDM Port line rate.
In the TXP direction the S132 supports all 3 techniques. The ACR technique is implicit in the packet transmit rate.
The DCR-DT and AT techniques are supported by transmitting Differential or Absolute Timestamps (respectively).
In the RXP direction the S132 directly supports the ACR and DCR-DT techniques. With the ACR technique the
Clock Recovery Engine recovers timing from the rate at which packets are received. With DCR-DT the Clock
Recovery Engine recovers timing from the received RTP Differential Timestamps.
In the RXP direction the S132 is compatible with (supports) the AT technique, but does not utilize the RTP Absolute
Timestamps. To provide compatibility with the AT technique the Clock Recovery Engine instead recovers timing
using the ACR technique (derived from the rate at which packets are received).
9.2.1.1.1 RXP Clock Recovery (RXP PW-Timing)
There are 32 RXP Clock Recovery Engines, one hardwired to each of the 32 TDM Ports. Each can be programmed
to support the ACR or DCR-DT technique.
Figure 9-8. Clock Recovery Engine Environment
DS34S132
RXP Timing
Xmt TDM Timing
TDM
Xmt Port
RXP Pkt
Classifier
RXP SAT/CES Engine Timing
Clock Recovery Engines
When a Transmit TDM Port is programmed to derive its timing from a Clock Recovery Engine, one TDMoP
PW/Bundle must be programmed to include an RXP PW-Timing Connection (B.BCDR4.PCRE). No more than one
PW/Bundle can be assigned to provide the RXP PW-Timing Connection for a TDM Port.
The RXP Clock Recovery technique (ACR or DCR-DT) is selected by properly programming the S132 Clock
Recovery Engine DSP firmware revision (not included in this Datasheet).
9.2.1.1.2 TXP PW-Timing
In the TXP direction the TDMoP PWs communicate timing information through the transmission rate of the TXP
Packets (ACR) and can optionally include an RTP Timestamp with each TXP Packet. TXP Packets are
automatically transmitted when sufficient T1/E1 data has been received to fill the TXP Packet payload. A TXP PW-
Timing Connection is only required if a TXP RTP Timestamp is included in the TXP packets.
The S132 appends a header to the payload of each TXP TDMoP Packet as it is transmitted. The header is
programmed using a TXP Header Descriptor that is stored in a block of memory at EMI.BMCR1.TXHSO (1 TXP
Header Descriptor per Bundle). A TXP PW-Timing Connection is enabled when the TXP Header Descriptor for a
Bundle is programmed to insert a TXP RTP Timestamp (TXRE field = 1; see “TXP SAT/CES and HDLC PW Packet
Generation” section). Any number of TXP Bundles can be programmed to include an RTP Header.
Figure 9-9. TXP PW-Timing Environment
DS34S132
TXP Timing
TXP Pkt
Generator
TXP SAT/CES Engine Timing
RTP Timestamp Generator
Rcv TDM Timing
TDM
Rcv Port
In the TXP direction, to conform to the Clock Recovery technique that is used at the far end PW end point, the
S132 allows the RTP Header to be optionally enabled with a Differential Timestamp or Absolute Timestamp,
independent of the RXP RTP settings. Pn.PRCR4.TSGMS selects whether Differential or Absolute Timestamps are
inserted when the RTP Header has been enabled in the TXP Header Descriptor.
RTP Differential Timestamp values are generated using the CMNCLK input and 3 coefficients that are programmed
in the Pn.PRCR4.TSGMC, Pn.PRCR5.TSGN1C and Pn.PRCR5.TSGN0C registers (programmed per TDM Port).
When the RTP Absolute Timestamp is enabled, the Absolute Timestamp values are incremented according to the
receive TDM Port timing (Pn.PRCR2.RSS selects the receive TDM Port timing as either RCLKn or TCLKOn).