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SL240 PROTOCOL
C.3.1 Link Bandwidth
With CRC disabled and the Copy Mode Master bit clear (‘0’), there is a five-word
overhead for every frame transmitted. Since frames can contain up to 512 words of data,
this results in an efficiency of 99.03%. With CRC enabled and the Copy Master bit clear,
there is a six-word overhead for every frame transmitted. This results in a maximum
efficiency of 98.84%. With the Copy Mode Master bit set (‘1’), three additional ordered
sets are added per frame. This results in an efficiency of 98.46 percent without CRC and
98.27 percent with CRC. Table C-2 gives the theoretical maximum sustained throughput
based on these numbers.
Table C-2 Maximum Sustained Throughput
Card
With CRC and
Copy Mode
Master bit = 0
Without CRC
and Copy Mode
Master bit = 0
With CRC and
Copy Mode
Master bit = 1
Without CRC and
Copy Mode
Master bit = 1
SL240
247.10 MB/s
247.58 MB/s
245.68 MB/s
246.15 MB/s
NOTE
: The Copy Master Mode is located in the Link Control register.
C.3.2 FPDP Signal Sample Rate
The states of the FPDP signals (PIO1, PIO2, DIR, and NRDY) are transmitted across the
link at varying rates. The worst-case rate at which these signals are sampled is for CRC
checked filled data frames and the Copy Mode Master bit set . In this case, the signals are
sampled every 521 words. For CRC checked filled data frames and the Copy Mode
Master bit clear, these signals are sampled every 518 words. Table C-3 summarizes the
worst-case sampling frequencies for the different link transmission speeds.
Table C-3 Sampling Frequencies
Card
With CRC and
Copy Mode
Master bit = 0
Without CRC
and Copy Mode
Master bit = 0
With CRC and
Copy Mode
Master bit = 1
Without CRC and
Copy Mode
Master bit = 1
SL240
120.65 KHz
120.89 KHz
119.96 KHz
120.19 KHz
NOTE
: The Copy Master Mode is located in the Link Control register.
Copyright 2006
C-4
FibreXtreme Hardware Reference Manual
Summary of Contents for FibreXtreme SL240
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