STANDARD PRODUCT
PM4328 TECT3
DATASHEET
PMC-2011596
ISSUE 1
HIGH DENSITY T1/E1 FRAMER
AND M13 MULTIPLEXER
SBI Timing Master Modes
The TECT3 supports both synchronous and asynchronous SBI timing modes.
Synchronous modes apply only to T1 tributaries and are used with ingress elastic
stores to rate adapt the receive tributaries to the fixed SBI data rate.
Asynchronous modes allow T1 and DS3 to float within the SBI structure to
accommodate differences in timing. Note that Synchronous mode SBI timing
operation is required for support of Channel Associated Signaling (CAS).
In synchronous SBI mode the T1 DS0s are in a fixed format and do not move
relative to the SBI structure. The SBI frame pulse, SC1FP, in synchronous mode
can be enabled to indicate CAS signaling multi-frame alignment by pulsing once
every 12th 2KHz SC1FP frame pulse period. SREFCLK sets the ingress rate from
the receive elastic store.
In Asynchronous modes timing is communicated across the Scaleable
Bandwidth Interconnect by floating data structures within the SBI. Payload
indicator signals in the SBI control the position of the floating data structure and
therefore the timing. When sources are running faster than the SBI the floating
payload structure is advanced by an octet be passing an extra octet in the V3
octet locations (H3 octet for DS3 mappings). When the source is slower than the
SBI bus, the floating payload is retarded by leaving the octet after the V3 or H3
octet unused. Both these rate adjustments are indicated by the SBI control
signals.
On the DROP BUS the TECT3 is timing master as determined by the arrival rate
of data over the SBI.
On the ADD BUS the TECT3 can be either the timing master or the timing slave.
When the TECT3 is the timing slave it receives its transmit timing information
from the arrival rate of data across the SBI ADD bus. When the TECT3 is the
timing master it signals devices on the SBI ADD bus to speed up or slow down
with the justification request signal, SAJUST_REQ. The TECT3 as timing master
indicates a speedup request to a Link Layer SBI device by asserting the
justification request signal high during the V3 or H3 octet. When this is detected
by the Link Layer it will speed up the channel by inserting extra data in the next
V3 or H3 octet. The TECT3 indicates a slowdown request to the Link Layer by
asserting the justification request signal high during the octet after the V3 or H3
octet. When detected by the Link Layer 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.
PROPRIETARY AND CONFIDENTIAL
159
PMC [ PMC-SIERRA, INC ]
