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Ed,
Yes, the CRC's which are on the bus are origonated by the host.
Possibly the confusion could be that UltraSCSI checks CRC on both ends.
It is symetrical, with the sender generating and sending the CRC and the
receiver generating and comparing the CRC.
In UltraDMA ( i.e. ATA) only the drive checks CRC (regardless of
direction). Both the host and the drive independantly generate CRC. But
in both read and write, the host sends it's CRC for the drive to compare
with it's own CRC. Only the drive can detect and report the CRC error.
...Harlan
On 9/5/01 Ed Fong <[EMAIL PROTECTED]> wrote:
>In section 6.6.1 of T13 1410D Revision 1b, the following sentence is
>mentioned.
>
>"At the end of an Ultra DMA burst the host sends its CRC data to the
>device. The device compares its CRC data to the data sent from the host.
>If the two values do not match, the device reports an error in the error
>register. ...."
>
>There appears to be many articles indicating that the CRC word is sent with
>the data, and the receiving end is the one performing the CRC check.
>
>Does the above statements specified in the specifications indicate that
>only the device shall receive the CRC data and perform the CRC check no
>matter what the data direction is (i.e. whether it is an ultra DMA read or
>ultra DMA write)? This implies that for any CRC information sent over the
>bus originates from the host?
>
>
>Thanks
>Ed
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