PCOMP_EN and Expanders

Mike Kosco Mike at ChipCraft.com
Wed Aug 29 12:16:40 PDT 2001

* From the T10 Reflector (t10 at t10.org), posted by:
* Mike Kosco <Mike at ChipCraft.com>
I have a couple questions regarding precomp and expanders relating to
the ECP annex in SPI-4.

Assuming the given IT nexus passes through the expander:

1. Is the expander's precomp assumed to be enabled via the passing of
ppr messages for the current IT assuming the IT both agree?  If so, I'm
assuming precomp is enabled on the near and far (target) port?

2. If precomp is not negotiated between a given IT, should the Margin
Control SEDB fields describing Driver Precompensation essentially be
disabled, as precomp is not enabled?

3.  In the Report Capabilities SEDB, why is bit 7 in the "protocol
option bits supported" field marked as reserved and not used to indicate
the expander's precomp support?

4. What is the use of the Near/Far/Sent/Recieved Pcomp_en bits defined
in the Report Current Status SEDB?

Mike Kosco
Need a SPI-4 expander core?
Chip Craft Corp.
(949) 633-8383

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