PM8621 datasheet(138/184 Pages) PMC

138 / 184 page

NSE-8G™ Standard Product Data Sheet

Preliminary

Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use

137

Document ID: PMC-2010850, Issue 1

Figure 18 “C1” Synchronization Control

Ingress SBI

device

Ingress SBS

(1 frame delay)

Egress SBS

(1 frame delay)

500

µs Source

delay

,t1

delay

125

µs

t at 0

µs

Egress SBI

device

delay

NSE

delay

125

µs

(no delay t delay through

Ingress SBI device)

12.3

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.

12.3.1 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.

PM8621 Datasheet(PDF) 138 Page - PMC-Sierra, Inc

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