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Re: Gryphon 68030 [message #2054 is a reply to message #2053]

Tue, 21 March 2017 10:22

norwestrzh
Messages: 196
Registered: November 2015

Senior Member

1) I've read that the 68K takes minimum of 4 clock cycles for memory access. If the ROM/SRAM on the board has an access time roughly equal to the clock period, is there ever any reason to delay DTACK? Slow I/O devices may need some delays but fast ROM/SRAM should be ready long before the 68K is. Am I missing something?

If you can find a copy of the Wilcox 68000 book, take a look at Figs. 7.12 and 7.16. The address bus isn't stable until the middle, or end, of the first clock cycle, and the address strobes (used for most memory access) aren't stable until the middle of the second clock cycle. The decision to assert DTACK* has to be made before the middle of the third clock cycle. So there is really only one clock cycle for data access.

2) For 8 bit I/O devices, there seems to be a wide variety of ways the 8 bit I/O devices is connected to the data lines. A lot of them seem to use the upper most byte on the data bus. The TS2 puts one 6850 on the high byte and the other 6850 on the low byte. Why do most people use the high data bus byte for accessing 8 bit devices?

I don't think there is any actual technical reason to choose the high or low data byte for 8-bit access. Maybe just convenience? One would require using even addresses, the other, odd addresses (for the 8-bit device). MOVEP can be used for 8-bit devices, and I don't believe there is any advantage for either even or odd addresses.

Roger

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[Message index]

		Gryphon 68030 By: lynchaj on Wed, 08 June 2016 13:57
		Re: Gryphon 68030 By: lynchaj on Wed, 08 June 2016 13:58
		Re: Gryphon 68030 By: computerdoc on Thu, 09 June 2016 01:43
		Re: Gryphon 68030 By: lynchaj on Fri, 10 June 2016 03:16
		Re: Gryphon 68030 By: computerdoc on Fri, 10 June 2016 08:56
		Re: Gryphon 68030 By: lynchaj on Fri, 10 June 2016 09:16
		Re: Gryphon 68030 By: yoda on Fri, 10 June 2016 10:46
		Re: Gryphon 68030 By: lynchaj on Fri, 10 June 2016 11:43
		Re: Gryphon 68030 By: yoda on Fri, 10 June 2016 11:49
		Re: Gryphon 68030 By: lynchaj on Fri, 10 June 2016 12:10
		Re: Gryphon 68030 By: yoda on Fri, 10 June 2016 12:24
		Re: Gryphon 68030 By: jcoffman on Fri, 10 June 2016 15:06
		Re: Gryphon 68030 By: will on Sat, 11 June 2016 03:29
		Re: Gryphon 68030 By: yoda on Sat, 11 June 2016 10:43
		Re: Gryphon 68030 By: lynchaj on Sun, 12 June 2016 04:15
		Re: Gryphon 68030 By: yoda on Sun, 12 June 2016 06:36
		Re: Gryphon 68030 By: lynchaj on Sun, 12 June 2016 07:03
		Re: Gryphon 68030 By: lynchaj on Sun, 12 June 2016 07:13
		Re: Gryphon 68030 By: yoda on Sun, 12 June 2016 08:07
		Re: Gryphon 68030 By: yoda on Sun, 12 June 2016 10:26
		Re: Gryphon 68030 By: lynchaj on Mon, 13 June 2016 04:58
		Re: Gryphon 68030 By: lynchaj on Tue, 14 June 2016 03:43
		Re: Gryphon 68030 By: will on Sun, 12 June 2016 16:52
		Re: Gryphon 68030 By: lynchaj on Sun, 12 June 2016 17:16
		Re: Gryphon 68030 By: yoda on Sun, 12 June 2016 18:06
		Re: Gryphon 68030 By: yoda on Sun, 12 June 2016 17:50
		Re: Gryphon 68030 By: will on Sun, 12 June 2016 07:27
		Re: Gryphon 68030 By: yoda on Sun, 12 June 2016 10:19
		Re: Gryphon 68030 By: Andrew B on Sun, 12 June 2016 10:48
		Re: Gryphon 68030 By: lynchaj on Sun, 12 June 2016 17:18
		Re: Gryphon 68030 By: lynchaj on Sun, 12 June 2016 17:40
		Re: Gryphon 68030 By: yoda on Sun, 12 June 2016 17:55
		Re: Gryphon 68030 By: Andrew B on Sun, 12 June 2016 18:05
		Re: Gryphon 68030 By: yoda on Sun, 12 June 2016 18:12
		Re: Gryphon 68030 By: Andrew B on Sun, 12 June 2016 18:30
		Re: Gryphon 68030 By: yoda on Sun, 12 June 2016 20:07
		Re: Gryphon 68030 By: lynchaj on Mon, 13 June 2016 03:22
		Re: Gryphon 68030 By: yoda on Mon, 13 June 2016 08:04
		Re: Gryphon 68030 By: lynchaj on Mon, 13 June 2016 09:17
		Re: Gryphon 68030 By: yoda on Mon, 13 June 2016 09:39
		Re: Gryphon 68030 By: Andrew B on Mon, 13 June 2016 09:59
		Re: Gryphon 68030 By: yoda on Mon, 13 June 2016 10:02
		Re: Gryphon 68030 By: lynchaj on Tue, 14 June 2016 03:18
		Re: Gryphon 68030 By: yoda on Tue, 14 June 2016 06:52
		Re: Gryphon 68030 By: lynchaj on Wed, 15 June 2016 17:36
		Re: Gryphon 68030 By: lynchaj on Thu, 16 June 2016 03:29
		Re: Gryphon 68030 By: lynchaj on Thu, 16 June 2016 03:34
		Re: Gryphon 68030 By: yoda on Thu, 16 June 2016 06:41
		Re: Gryphon 68030 By: lynchaj on Thu, 16 June 2016 08:29
		Re: Gryphon 68030 By: lynchaj on Sat, 18 June 2016 08:38
		Calling on logic equation gurus By: yoda on Fri, 24 June 2016 08:50
		Re: Calling on logic equation gurus By: Andrew B on Fri, 24 June 2016 09:46
		Re: Calling on logic equation gurus By: yoda on Fri, 24 June 2016 11:14
		All: Please review verilog code By: yoda on Fri, 24 June 2016 17:41
		Re: All: Please review verilog code By: lynchaj on Sun, 26 June 2016 13:40
		Re: All: Please review verilog code By: lynchaj on Sun, 26 June 2016 13:44
		Re: All: Please review verilog code By: Andrew B on Mon, 27 June 2016 09:51
		Re: All: Please review verilog code By: lynchaj on Mon, 27 June 2016 11:36
		Re: All: Please review verilog code By: yoda on Mon, 27 June 2016 12:25
		Re: All: Please review verilog code By: lynchaj on Tue, 28 June 2016 03:21
		Re: All: Please review verilog code By: jcoffman on Tue, 28 June 2016 03:29
		Re: All: Please review verilog code By: lynchaj on Tue, 28 June 2016 03:55
		Re: All: Please review verilog code By: yoda on Sun, 26 June 2016 17:02
		Re: All: Please review verilog code By: lynchaj on Mon, 27 June 2016 03:42
		Re: Gryphon 68030 By: lynchaj on Tue, 28 June 2016 15:51
		Re: Gryphon 68030 By: yoda on Tue, 28 June 2016 17:07
		Re: Gryphon 68030 By: lynchaj on Wed, 29 June 2016 03:32
		Re: Gryphon 68030 By: jcoffman on Wed, 29 June 2016 08:01
		Re: Gryphon 68030 By: lynchaj on Wed, 29 June 2016 09:15
		Re: Gryphon 68030 By: lynchaj on Wed, 29 June 2016 16:37
		Re: Gryphon 68030 By: lynchaj on Fri, 08 July 2016 08:18
		Re: Gryphon 68030 By: lynchaj on Sat, 09 July 2016 06:57
		Re: Gryphon 68030 By: lynchaj on Mon, 18 July 2016 17:52
		Re: Gryphon 68030 By: lynchaj on Sat, 23 July 2016 11:56
		Re: Gryphon 68030 By: davetypeguy on Mon, 25 July 2016 10:16
		Re: Gryphon 68030 By: yoda on Mon, 25 July 2016 13:39
		Re: Gryphon 68030 By: davetypeguy on Mon, 25 July 2016 14:46
		Re: Gryphon 68030 By: lynchaj on Tue, 26 July 2016 13:50
		Re: Gryphon 68030 By: lynchaj on Fri, 03 February 2017 05:05
		Re: Gryphon 68030 By: lynchaj on Sat, 04 February 2017 10:23
		Re: Gryphon 68030 By: Andrew B on Sat, 04 February 2017 11:28
		Re: Gryphon 68030 By: computerdoc on Fri, 10 February 2017 02:17
		Re: Gryphon 68030 By: will on Fri, 10 February 2017 03:56
		Re: Gryphon 68030 By: lynchaj on Sat, 11 February 2017 07:19
		Re: Gryphon 68030 By: will on Sat, 11 February 2017 13:20
		Re: Gryphon 68030 By: Andrew B on Sat, 11 February 2017 13:31
		Re: Gryphon 68030 By: lynchaj on Sat, 11 February 2017 13:52
		Re: Gryphon 68030 By: yoda on Sat, 11 February 2017 14:05
		Re: Gryphon 68030 By: will on Sat, 11 February 2017 14:44
		Re: Gryphon 68030 By: computerdoc on Fri, 10 February 2017 02:25
		Re: Gryphon 68030 By: lynchaj on Sat, 11 February 2017 07:06
		Re: Gryphon 68030 By: computerdoc on Sat, 11 February 2017 19:00
		Re: Gryphon 68030 By: lynchaj on Sat, 11 February 2017 08:14
		Re: Gryphon 68030 By: davetypeguy on Sun, 12 February 2017 00:22
		Re: Gryphon 68030 By: yoda on Sun, 12 February 2017 10:52
		Re: Gryphon 68030 By: lynchaj on Sun, 12 February 2017 11:11
		Re: Gryphon 68030 By: Garth on Mon, 13 February 2017 02:07
		Re: Gryphon 68030 By: Andrew B on Fri, 17 February 2017 14:47
		Re: Gryphon 68030 By: denis2342 on Tue, 28 February 2017 06:27
		Re: Gryphon 68030 By: yoda on Tue, 28 February 2017 06:48
		Re: Gryphon 68030 By: denis2342 on Tue, 28 February 2017 07:12
		Re: Gryphon 68030 By: yoda on Tue, 28 February 2017 07:40
		Re: Gryphon 68030 By: will on Tue, 28 February 2017 14:55
		Re: Gryphon 68030 By: denis2342 on Thu, 02 March 2017 20:32
		Re: Gryphon 68030 By: ewout on Fri, 03 March 2017 02:54
		Re: Gryphon 68030 By: lynchaj on Fri, 03 March 2017 03:51
		Re: Gryphon 68030 By: lynchaj on Fri, 03 March 2017 03:54
		Re: Gryphon 68030 By: lynchaj on Mon, 06 March 2017 03:00
		Re: Gryphon 68030 By: ewout on Thu, 09 March 2017 00:58
		Re: Gryphon 68030 By: lynchaj on Thu, 09 March 2017 07:05
		Re: Gryphon 68030 By: lynchaj on Thu, 09 March 2017 07:07
		Re: Gryphon 68030 By: yoda on Thu, 09 March 2017 07:16
		Re: Gryphon 68030 By: ewout on Thu, 09 March 2017 07:33
		Re: Gryphon 68030 By: lynchaj on Thu, 09 March 2017 07:52
		Re: Gryphon 68030 By: yoda on Thu, 09 March 2017 11:50
		Re: Gryphon 68030 By: lynchaj on Thu, 09 March 2017 11:59
		Re: Gryphon 68030 By: yoda on Thu, 09 March 2017 12:32
		Re: Gryphon 68030 By: lynchaj on Thu, 09 March 2017 15:25
		Re: Gryphon 68030 By: yoda on Thu, 09 March 2017 16:01
		Re: Gryphon 68030 By: lynchaj on Thu, 09 March 2017 16:26
		Re: Gryphon 68030 By: yoda on Thu, 09 March 2017 17:13
		Re: Gryphon 68030 By: lynchaj on Fri, 10 March 2017 02:56
		Re: Gryphon 68030 By: yoda on Fri, 10 March 2017 07:52
		Re: Gryphon 68030 By: lynchaj on Fri, 10 March 2017 08:31
		Re: Gryphon 68030 By: lynchaj on Sat, 11 March 2017 05:56
		Re: Gryphon 68030 By: lynchaj on Sat, 11 March 2017 06:13
		Re: Gryphon 68030 By: mikemac on Sat, 11 March 2017 12:30
		Re: Gryphon 68030 By: yoda on Sat, 11 March 2017 12:43
		Re: Gryphon 68030 By: mikemac on Sat, 11 March 2017 14:41
		Re: Gryphon 68030 By: lynchaj on Sun, 12 March 2017 05:21
		Re: Gryphon 68030 By: lynchaj on Sun, 12 March 2017 09:20
		Re: Gryphon 68030 By: lynchaj on Sun, 12 March 2017 10:28
		Re: Gryphon 68030 By: mikemac on Sun, 12 March 2017 14:14
		Re: Gryphon 68030 By: lynchaj on Sun, 12 March 2017 14:34
		Re: Gryphon 68030 By: mikemac on Sun, 12 March 2017 17:40
		Re: Gryphon 68030 By: lynchaj on Mon, 13 March 2017 02:55
		Re: Gryphon 68030 By: lynchaj on Mon, 13 March 2017 05:43
		Re: Gryphon 68030 By: lynchaj on Wed, 15 March 2017 02:54
		Re: Gryphon 68030 By: davetypeguy on Wed, 15 March 2017 09:06
		Re: Gryphon 68030 By: lynchaj on Sat, 11 March 2017 13:00
		Re: Gryphon 68030 By: lynchaj on Sat, 11 March 2017 13:12
		Re: Gryphon 68030 By: yoda on Sat, 11 March 2017 13:23
		Re: Gryphon 68030 By: mikemac on Sat, 08 April 2017 19:59
		Re: Gryphon 68030 By: rhkoolstar on Sat, 08 April 2017 23:27
		Re: Gryphon 68030 By: plasmo on Sun, 09 April 2017 05:32
		Re: Gryphon 68030 By: tobster on Wed, 15 March 2017 13:08
		Re: Gryphon 68030 By: yoda on Wed, 15 March 2017 14:02
		Re: Gryphon 68030 By: lynchaj on Thu, 16 March 2017 13:52
		Re: Gryphon 68030 By: mikemac on Tue, 21 March 2017 09:55
		Re: Gryphon 68030 By: norwestrzh on Tue, 21 March 2017 10:22
		Re: Gryphon 68030 By: yoda on Tue, 21 March 2017 10:46
		Re: Gryphon 68030 By: lynchaj on Thu, 23 March 2017 05:44
		Re: Gryphon 68030 By: lynchaj on Sat, 25 March 2017 06:30
		Re: Gryphon 68030 By: lynchaj on Sat, 25 March 2017 08:03
		Re: Gryphon 68030 By: mikemac on Sat, 25 March 2017 16:19
		Re: Gryphon 68030 By: jcoffman on Sat, 25 March 2017 18:07
		Re: Gryphon 68030 By: mikemac on Sat, 25 March 2017 21:05
		Re: Gryphon 68030 By: yoda on Sun, 26 March 2017 08:32
		Re: Gryphon 68030 By: tobster on Sun, 26 March 2017 02:25
		Re: Gryphon 68030 By: mikemac on Sun, 26 March 2017 09:18
		Re: Gryphon 68030 By: lynchaj on Sun, 26 March 2017 09:47
		Re: Gryphon 68030 By: mikemac on Mon, 27 March 2017 09:18
		Re: Gryphon 68030 By: lynchaj on Mon, 27 March 2017 09:30
		Re: Gryphon 68030 By: mikemac on Thu, 30 March 2017 10:13
		Re: Gryphon 68030 By: lynchaj on Thu, 30 March 2017 10:46
		Re: Gryphon 68030 By: mikemac on Thu, 30 March 2017 11:56
		Re: Gryphon 68030 By: Andrew B on Thu, 30 March 2017 13:50
		Re: Gryphon 68030 By: mikemac on Thu, 30 March 2017 14:03
		Re: Gryphon 68030 By: mikemac on Thu, 30 March 2017 14:37
		Re: Gryphon 68030 By: tingo on Mon, 03 April 2017 13:44
		Re: Gryphon 68030 By: mikemac on Mon, 03 April 2017 15:28
		Re: Gryphon 68030 By: lynchaj on Tue, 04 April 2017 04:02
		Re: Gryphon 68030 By: mikemac on Tue, 04 April 2017 07:50
		Re: Gryphon 68030 By: lynchaj on Fri, 07 April 2017 04:31
		Re: Gryphon 68030 By: rhkoolstar on Sat, 08 April 2017 11:30
		Re: Gryphon 68030 By: lynchaj on Sat, 08 April 2017 11:46
		Re: Gryphon 68030 By: mikemac on Sat, 08 April 2017 12:48
		Re: Gryphon 68030 By: plasmo on Sun, 09 April 2017 20:22
		Re: Gryphon 68030 By: rhkoolstar on Sun, 09 April 2017 23:16
		Re: Gryphon 68030 By: lynchaj on Mon, 10 April 2017 03:00
		Re: Gryphon 68030 By: lynchaj on Mon, 10 April 2017 03:18
		Re: Gryphon 68030 By: plasmo on Mon, 10 April 2017 12:38
		Re: Gryphon 68030 By: commodorejohn on Mon, 17 April 2017 15:14
		Re: Gryphon 68030 By: lynchaj on Tue, 18 April 2017 04:21
		Re: Gryphon 68030 By: yoda on Tue, 18 April 2017 07:04
		Re: Gryphon 68030 By: lynchaj on Tue, 18 April 2017 08:57
		Re: Gryphon 68030 By: yoda on Tue, 18 April 2017 09:53
		Re: Gryphon 68030 By: commodorejohn on Tue, 18 April 2017 09:59
		Re: Gryphon 68030 By: lynchaj on Tue, 18 April 2017 11:35
		Re: Gryphon 68030 By: mikemac on Tue, 18 April 2017 16:48
		Re: Gryphon 68030 By: lynchaj on Tue, 18 April 2017 17:47
		Re: Gryphon 68030 By: lynchaj on Wed, 19 April 2017 02:55
		Re: Gryphon 68030 By: yoda on Wed, 19 April 2017 14:15
		Re: Gryphon 68030 By: lynchaj on Wed, 19 April 2017 15:56
		Re: Gryphon 68030 By: mikemac on Thu, 20 April 2017 11:15
		Re: Gryphon 68030 By: lynchaj on Thu, 20 April 2017 12:05
		Re: Gryphon 68030 By: mikemac on Thu, 20 April 2017 12:33
		Re: Gryphon 68030 By: lynchaj on Thu, 20 April 2017 15:58
		Re: Gryphon 68030 By: mikemac on Thu, 20 April 2017 16:51
		Re: Gryphon 68030 By: lynchaj on Fri, 21 April 2017 02:54
		Re: Gryphon 68030 By: yoda on Fri, 21 April 2017 08:54
		Re: Gryphon 68030 By: lynchaj on Fri, 21 April 2017 09:14
		Re: Gryphon 68030 By: yoda on Fri, 21 April 2017 11:15
		Re: Gryphon 68030 By: lynchaj on Fri, 21 April 2017 12:02
		Re: Gryphon 68030 By: plasmo on Mon, 10 April 2017 12:31

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