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Some hosts implement an edge-triggered interrupt on the INTRQ line and implement a pull-up of 10K. The hardware and/or software is prepared to deal with the positive edge that happens when the drive(s) release the interrupt line. Other hosts implement a pull-down and treat the line as either edge or level trigger. These hosts prefer not to deal with the false assertion when the drive(s) release the INTRQ line. Beyond that, hosts have been built with every combination from no resistor at all to any number of values of pull-up/down resistors. To me, a pull down makes the most sense. The only issue is leakage current in the release (tri-state) mode, when the host implements a pull-down, which is why I wrote e01119r0. At 7:42 AM -0700 9/28/01, Evans, Mark wrote: >Hi Keith, > >I know of at least two different host-side implementations for sensing >INTRQ. One implementation uses a positive going, edge-triggered receiving >device. This implementation requires a pull-up resistor so that there will >be no positive-going glitch when INTRQ is released (nIEN set to one, or >between the time one device releases INTRQ before the other device negates >INTRQ). The second implementation uses a positive level sensing receiving >device. This implementation requires a pull-down resistor so that there >will be no positive level sensed for any reason except when actually >asserted by a device. > >I am also attaching a proposal to specify the leakage current on INTRQ >(e01119r0) that I expect will be accepted at the next meeting for inclusion >in ATA/ATAPI-7. I hope this helps. Please feel free to call or send an >email to me if you have any additional questions. > >Regards, > >Mark Evans >Maxtor Corporation >500 McCarthy Boulevard >Milpitas, CA 95035 USA >Tel: 408-894-5310 >FAX: 408-324-7432 >email: [EMAIL PROTECTED] > > <<e01119r0.pdf>> > -----Original Message----- >From: Keith Clausen [mailto:[EMAIL PROTECTED]] >Sent: Friday, September 28, 2001 1:04 AM >To: [EMAIL PROTECTED]; [EMAIL PROTECTED] >Subject: ANSI NCITS 340-2000 (ATAPI-5): INTRQ > >Thanks Mark, I shall go away and digest your comments. Unfortunately, we at >ST >are having trouble viewing the reflector at the moment, so most effective >response currently is to copy me directly at [EMAIL PROTECTED] (assuming >people on the reflector will also be interested in answers). > >Since you seem to understand this so well, could you perhaps enlighten me on >another aspect of the std that is a bit of a mystery: > >ANSI NCITS 340-2000 (ATAPI-5): Page 11 Section 4.2.1 Table 5 Note 5 (INTRQ) > >"A 10K pull-down or pull-up, depending upon the level sensed should be >implemented at the host." > >What does this mean?! INTRQ is always active high (by naming convention) and >I >assume all devices adhere to this. If not..... no, really - it wouldn't make >sense! > >I can see why a pull-down might be required (to ensure there is no spurious >active INTRQ when devices are switched), but I don't see a case for pull-up. >Whatever - what does "depending upon the level sensed" mean? > >Cheers > >K > > >-- >Keith Clausen, STMicroelectronics, >Mail: 1000 Aztec West, Bristol BS32 4SQ, UK >Email: [EMAIL PROTECTED] >Phone: +44 1454 462457 Fax: +44 1454 617910 > > >Attachment converted: FreddyKing:e01119r0.pdf (PDF /CARO) (0000BF05) -- --------------------- "Anything you CAN control you MUST control." Wendy Carlos --------------------- Larry Barras Apple Computer Inc. 1 Infinite Loop MS: 306-2TC Cupertino, CA 95014 (408) 974-3220 -- If you have any questions or wish to unsubscribe send a message to Hale Landis, [EMAIL PROTECTED] To post to this list server send your message to [EMAIL PROTECTED] For questions concerning Thistle Grove Industries or TGI's list services please send email to [EMAIL PROTECTED]
