PM8621 PMC-Sierra, Inc., PM8621 Datasheet - Page 143

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

12.4
Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use
Document ID: PMC-2010850, Issue 1
Figure 24 Non DS0 Switch Timing
SBS#2 OCMP.INT
NSE-8G CPU Interaction with the Switching Cycle When Using
the ILC
An interrupt is made available to the NSE-8G CPU called the Frame Interrupt this occurs at the
start of the internal frame and marks a time in the NSE-8G where updates to the system page bits
can occur. This interrupt is maskable and would normally be masked.
The CPU will need to enable this interrupt before a page switch is required, then respond to this
interrupt immediately and complete writing the new page bit settings (a two double word
operation) within 27 µs.
This is required as the ILC will sample the SBS page bits (in the ILCs) once during the frame
before the first message is assembled and sent (starting at the beginning of row 3). If the page bits
are updated late, the SBS pages will switch a frame late, which means the NSE-8G DCB may
switch early giving disastrous results.
The NSE-8G CPU will have the rest of the frame to signal a page switch to the DCB as this is
sampled on the next frame
SBS#1 TCMP.INT
NSE RC1FP.INT
SBI Frame Time
SBS RC1FP.INT
SBS OC1FP.INT
SBS IC1FP.INT
SBS#2 OCMP
NSE CMP.INT
SBS#1 TCMP
Internal Sigs
NSE CMP
C1FP
0us
250us
NSE-8G™ Standard Product Data Sheet
500us
Preliminary
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