Just to clarify the reasoning behind this. The device has a method of reporting errors (i.e. the ERR bit in the status register and the ERROR register). There is no standard method for the host adapter to report an error and be understood by EXISTING software. The method chosen allows existing software (assuming it checks for errors) to detect an error no matter which direction the data is sent.
-----Original Message-----
From: Stegmier, Steve [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, September 05, 2001 2:04 PM
To: '[EMAIL PROTECTED]'
Subject: [temp t13] Re: Ultra DMA CRC Clarification
** This is the quasi-official and semi-temporary T13 email list server. **
Indeed, regardless of the direction of data transfer, both host and device
calculate CRC on the data transferred, the host sends its CRC data, and the
device compares the host CRC against the device calculated CRC value.
Steve Stegmier
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, September 05, 2001 2:23 PM
To: [EMAIL PROTECTED]
Subject: [temp t13] Ultra DMA CRC Clarification
** This is the quasi-official and semi-temporary T13 email list server. **
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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