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Mark, A device (or host) can terminate a burst at any time, for whatever reason, by following the protocol in the standard. I'd strongly advise against reading anything into that event other than that the device/host did not want to transfer more data at that time. If the command is to continue, then eventually another burst will be initiated (once again, as specified in the standard). If not, then the command can be terminated as per the standard (typically with a device posting status after getting the host's attention, with an interrupt if they are enabled). The key thing here is just to treat your implementation as a state machine - there is no need to understand why something happens, just embody the protocol in the standard. Note that while the bus is clear (i.e. no burst active), other activity can take place - this is covered in the overlapped and queued commands. But as I said, this is just one of a lot of possible reasons for multiple bursts during a command. Jim -----Original Message----- From: Mark Sawyer [mailto:[EMAIL PROTECTED]] Sent: Wednesday, April 03, 2002 8:59 AM To: [EMAIL PROTECTED] Subject: [t13] UDMA Bursts - Pause versus Termination This message is from the T13 list server. Hello, T13: The question of pausing versus terminating a UDMA burst has come up on a project I am involved with and I would like to ask the T13 reflector to help me understand the differences. The project involves custom IDE/ATA/ATAPI hardware and in-house firmware development. I have read the relevent sections of the ATA/ATAPI-6 specification (paragraph 6.6.2). As I understand it, a UDMA burst termination is not the same as command termination so it would seem to me that the intention of the device would probably be to complete the command under normal circumstances. I would like to know under what conditions a device would typically terminate a UDMA burst. Is there a benefit of one method over the other? Is it common for a device to choose burst termination as a method of flow control? Assuming that a device terminates a burst, would it be safe to say that the HOST could choose to utilize I/O resources for I/O with other devices whereas during a pause the ATA bus is still dedicated to UDMA with the device? Thanks, /mbs --- Mark Sawyer Sawyer Software Solutions, LLC 2 Lincoln Drive, Bow, NH 03304-3209 Tel: 603-228-9214 / Cell: 603-496-3509 / FAX: 603-228-4810 --- AOL's AIM: FirmwareWizard
