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With DMA the HOST DOES NOT NEED to know the amount of data to transfer before the device starts transferring data. In all cases the device can halt the transfer of data when it runs out by terminating the DMA burst. The device indicates that all of the data has been transferred for the command by terminating the burst and asserting INTRQ. If you want to use odd byte counts for a command then PIO still makes some sense, but none of the sector sizes we've been discussing have that problem (for read/write of user data). Jim -----Original Message----- From: Pat LaVarre [mailto:[EMAIL PROTECTED]] Sent: Friday, January 25, 2002 5:05 PM To: [EMAIL PROTECTED] Subject: [t13] just use Pio This message is from the T13 list server. > [EMAIL PROTECTED] 01/25/02 08:43AM > Just use PIO ... In passing I happened to notice Hale is here restating a part of Jan 1996 Sff8020i rev 2.6 paragraph 5.4 that I think I remember never made its way into Ansi texts. Long time listeners to this reflector surely will find the spectacle of Hale & Sff agreeing something like as amusing as I do? I quote: "For some commands, such as Mode Sense, the Host does not know the amount of data that will be transferred, and shall rely on the Byte Count supplied by the Device to transfer the correct amount of data. > Just use PIO ... Wish I could, wish I could, wish I could, but Ansi Pio development stopped cold way back at the 17e+6 byte/s of Pio4. Pat LaVarre Subscribe/Unsubscribe instructions can be found at www.t13.org. Subscribe/Unsubscribe instructions can be found at www.t13.org.
