PM8621 PMC-Sierra, Inc., PM8621 Datasheet - Page 138

• Manufacturer Part Number: PM8621
• Description: NSE-8G Standard Product Data Sheet Preliminary
• Manufacturer: PMC-Sierra, Inc.

12.3
12.3.1
Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use
Document ID: PMC-2010850, Issue 1
Figure 18 “C1” Synchronization Control
Synchronized Control Setting Changes
The NSE-8G and SBS support dual switch control settings. These dual settings permit one bank
of settings to be operational while the other bank is updated as a result of some new connection
requests. The CMP input selects the current operational switch control settings. CMP is sampled
by the NSE-8G on the RC1FP. The internal blocks sample the registered CMP value as they
receive the next C1 character after a delay of RC1DLY. The new CMP value is applied on the first
A1 character of the following STS-12 frame. This switchover is hitless; the control change does
not disrupt the user data flow in any way. This feature is required for the addition of arbitrary new
connections, as existing connections may need to be rerouted (see the discussion of the
connection routing algorithm in this document).
The DS0-granularity switch settings RAM in organized into two control settings banks, these are
switched by the above mechanisms on C1 boundaries. The NSE-8G also has to coordinate the
switching of the connected SBS devices (if using the In-Band link facility), so a broader
understanding of the issues is required.
The following sections provide examples.
SBS/NSE-8G Systems with DS0 and CAS Switching
When building a DS0 and Channel Associated Signaling switching system with the SBS, SBS-lite
and NSE-8G devices the overall timing is based on the CAS signaling multiframe on the SBI bus.
In this configuration the delay through the SBS devices is a single 125 µS SBI frame plus a few
77.76 MHz clocks and the delay through the NSE-8G is a few 77.76 MHz clocks. A single C1FP
frame synchronization signal is distributed around the system. Internal to the SBS and NSE-8G
devices are programmable offsets used to account for propagation delays through the system. The
key constraint is that all SBI frames are aligned going into the NSE-8G device.
Compatible devices are TEMUX-84, FREEDM-336, FREEDM-336-84 bond-out, S/UNI-IMA-
84, and other future SBI336 devices.
t
0
Ingress SBI
device
t at 0 s
t
0
,
t
1
delay
(no delay t delay through
t
1
Ingress SBI device)
(1 frame delay)
Ingress SBS
125 s
delay
delay
t
2
500 s Source
t
2
NSE
t
3
delay
t
3
NSE-8G™ Standard Product Data Sheet
125 s
delay
(1 frame delay)
Egress SBS
t
4
delay
t
4
Egress SBI
device
Preliminary
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