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RELEASED
PM73122 AAL1GATOR-32
DATASHEET
PMC-1981419
ISSUE 7
32 LINK CES/DBCES AAL1 SAR PROCESSOR
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
170
inserting data in the next V3 or H3 octet as described above. The PHY timing
master indicates a slowdown request to the Line Interface Block by asserting the
justification request signal (AJUST_REQ) high during the octet after the V3 or H3
octet. When detected by the Line Interface Block it will retard the channel by
leaving the octet following the next V3 or H3 octet unused. Both advance and
retard rate adjustments take place in the frame or multi-frame following the
justification request.
11.6.3.1.5
Jitter
The Scaleable Bandwidth Interconnect is a time division multiplexed bus and as
such, introduces jitter into the transported signal. Although ideal for datacom
applications, care needs to be taken when using the SBI for some jitter sensitive
applications.
Link rate information can optionally be carried across the SBI on a per link basis.
Two methods are specified, one for T1 and E1 channels and the second for DS3
channels. These methods use REFCLK and the C1FP frame synchronization
signal to measure channel clock ticks and clock phase for transport across the
bus.
The T1 and E1 method allows for a count of the number of T1 or E1 rising clock
edges between two C1FP frame pulses. This count is encoded in ClkRate[1:0] to
indicate that the nominal number of clocks, one more than nominal or one less
than nominal should be generated during the C1FP period. This method also
counts the number of REFCLK edges after sampling C1FP low to the next rising
edge of the T1 or E1 clock, giving the ability to control the phase of the
generated clock. The link rate information is passed across the SBI bus via the
V4 octet and is shown in Figure 79. Table 11 shows the encoding of the clock
count, ClkRate[1:0], passed in the link rate octet.
Figure 79 T1/E1 Link Rate Information
C1FP
REFCLK
T1/E1 CLK
Clock Count
Phase