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Re: ECB-DMA [message #6868 is a reply to message #6867]

Thu, 12 December 2019 21:24

wsm
Messages: 232
Registered: February 2017
Location: AB, Canada

Senior Member

I don't have any of the ECB cards so won't comment on that interface. However, I did develop a SCSI interface board for my NYOZ system using the Z53C80 which is the CMOS version of the Z5380 / NCR5380. A couple of comments:

Termination takes a LOT of current and is one more potential configuration problem, especially when devices are added / removed from the chain or powered down. I chose to use active termination based on the UCC5606 which also has the advantage of offering 2.5K Ohm versus 110 Ohm termination for short cable runs.

I'm not sure which processor you intend to use but the 53*80 requires a relatively long data hold after the IOW* goes inactive: 30/40 ns for the 5380 and 20/25 ns for the 53C80 (CPU write/DMA write).

Note that the datasheet discusses block-mode DMA restrictions and does not recommend using this mode due to the difficulty in detecting when there are SCSI bus errors.

If using the Z180's DMA channels, it should be noted that on DMA reads they generate the TEND signal on the last DMA memory write, and not on the I/O read as the peripheral would expect. Although I see the XFER_END# signal going into your 5380's EOP#, it's not obvious to me where it's actually coming from.

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[Message index]

		ECB-DMA By: b1ackmai1er on Sun, 10 November 2019 00:16
		Re: ECB-DMA By: Wayne W on Tue, 12 November 2019 12:31
		Re: ECB-DMA By: jcoffman on Tue, 12 November 2019 16:14
		Re: ECB-DMA By: etchedpixels on Wed, 13 November 2019 15:40
		Re: ECB-DMA By: b1ackmai1er on Fri, 15 November 2019 20:34
		Re: ECB-DMA By: b1ackmai1er on Sat, 16 November 2019 04:56
		Re: ECB-DMA By: etchedpixels on Sat, 16 November 2019 05:23
		Re: ECB-DMA By: jcoffman on Sat, 16 November 2019 08:03
		Re: ECB-DMA By: wsm on Sat, 16 November 2019 09:28
		Re: ECB-DMA By: jcoffman on Sat, 16 November 2019 13:09
		Re: ECB-DMA By: wsm on Sat, 16 November 2019 14:02
		Re: ECB-DMA By: b1ackmai1er on Sun, 17 November 2019 05:50
		Re: ECB-DMA By: jcoffman on Sun, 17 November 2019 07:06
		Re: ECB-DMA By: etchedpixels on Sun, 17 November 2019 07:41
		Re: ECB-DMA By: wsm on Sun, 17 November 2019 10:06
		Re: ECB-DMA By: wsm on Sun, 17 November 2019 14:12
		Re: ECB-DMA By: jcoffman on Sun, 17 November 2019 21:28
		Re: ECB-DMA By: rcini on Thu, 12 December 2019 17:52
		Re: ECB-DMA By: wsm on Thu, 12 December 2019 21:24
		Re: ECB-DMA By: rcini on Fri, 13 December 2019 07:22
		Re: ECB-DMA By: mikesmith on Thu, 09 January 2020 18:36
		Re: ECB-DMA By: wsm on Thu, 09 January 2020 20:28
		Re: ECB-DMA By: lynchaj on Mon, 26 April 2021 09:03
		Re: ECB-DMA By: lynchaj on Tue, 27 April 2021 04:41
		Re: ECB-DMA By: lynchaj on Wed, 28 April 2021 08:00
		Re: ECB-DMA By: jcoffman on Sat, 16 November 2019 07:56
		Re: ECB-DMA By: jcoffman on Sat, 16 November 2019 07:45
		Re: ECB-DMA By: b1ackmai1er on Thu, 17 June 2021 07:14
		Re: ECB-DMA By: lynchaj on Thu, 17 June 2021 07:29
		Re: ECB-DMA By: b1ackmai1er on Sat, 19 June 2021 05:33
		Re: ECB-DMA By: lynchaj on Sat, 19 June 2021 07:11
		Re: ECB-DMA By: lynchaj on Sat, 19 June 2021 07:30
		Re: ECB-DMA By: b1ackmai1er on Mon, 21 June 2021 07:31
		Re: ECB-DMA By: b1ackmai1er on Sat, 26 June 2021 19:10
		Re: ECB-DMA By: b1ackmai1er on Fri, 02 July 2021 02:06
		Re: ECB-DMA By: lynchaj on Fri, 02 July 2021 04:49
		Re: ECB-DMA By: b1ackmai1er on Fri, 02 July 2021 07:23
		Re: ECB-DMA By: etchedpixels on Thu, 08 July 2021 08:22
		Re: ECB-DMA By: b1ackmai1er on Fri, 09 July 2021 22:08
		Re: ECB-DMA By: lynchaj on Tue, 13 July 2021 11:44
		Re: ECB-DMA By: lynchaj on Thu, 29 July 2021 12:15
		Re: ECB-DMA By: b1ackmai1er on Sun, 04 July 2021 08:09
		Re: ECB-DMA By: b1ackmai1er on Mon, 05 July 2021 07:35
		Re: ECB-DMA By: lynchaj on Wed, 07 July 2021 03:27
		Re: ECB-DMA By: lynchaj on Wed, 07 July 2021 03:44
		Re: ECB-DMA By: lynchaj on Mon, 14 March 2022 03:48
		Re: ECB-DMA By: lynchaj on Wed, 23 March 2022 10:05

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