Hi Guys,
I tested the FPMini with the original IMSAI 8080 CPU board, Big-Z Z80 board and my 8080 replacement board.
It worked 100% fine with the 8080 boards. With the Big-Z Z80 board, there was a minor issue with reflections on the pSYNC line, which got resolved by adding a terminating resistor. These tests were done on my IMSAI without any termination, this might not be a problem if you have an actively terminated S-100 bus. It was interesting to see that the same problem existed when using the Big-Z / FPMini combo and the Big-Z / IMSAI FP combo. I wonder if anyone in the 70's documented the problem?
The exact problem was reflections on the pSYNC line caused the EXAMINE micro code counter (a JMP instruction) to skip ahead. Thus the "EXAMINE" switch displayed the wrong address.
The fix was to use a resistor to cancel those reflections, or use a 74HCT04 chip which has better noise rejection on the inputs. I think I even tried some 74LS14's with success.
Regards,
Josh
Date: Fri, 1 Aug 2014 12:24:27 -0700
Subject: Re: [N8VEM-S100:4777] Re: Announcing FPMini - IMSAI Style front Panel Reproduction
From: cap...@uxpro.com
To: n8vem...@googlegroups.com
--
-------------------------------
Don Caprio cap...@uxpro.com
http://www.uxpro.com
(925) 240-UNIX
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I tested the FPMini with the original IMSAI 8080 CPU board, Big-Z Z80 board and my 8080 replacement board.
It worked 100% fine with the 8080 boards. With the Big-Z Z80 board, there was a minor issue with reflections on the pSYNC line, which got resolved by adding a terminating resistor. These tests were done on my IMSAI without any termination, this might not be a problem if you have an actively terminated S-100 bus. It was interesting to see that the same problem existed when using the Big-Z / FPMini combo and the Big-Z / IMSAI FP combo. I wonder if anyone in the 70's documented the problem?
The exact problem was reflections on the pSYNC line caused the EXAMINE micro code counter (a JMP instruction) to skip ahead. Thus the "EXAMINE" switch displayed the wrong address.
The fix was to use a resistor to cancel those reflections, or use a 74HCT04 chip which has better noise rejection on the inputs. I think I even tried some 74LS14's with success.
Regards,
Josh
Date: Fri, 1 Aug 2014 12:24:27 -0700
Subject: Re: [N8VEM-S100:4777] Re: Announcing FPMini - IMSAI Style front Panel Reproduction
From: cap...@uxpro.com
To: n8vem...@googlegroups.com
Should work on 8080 and Z80
On Fri, Aug 1, 2014 at 11:50 AM, Andrew Bingham <abin...@gmail.com> wrote:
What CPUs will this work with? 8080? Z80?
On Friday, August 1, 2014 10:57:04 AM UTC-7, Don Caprio wrote:
Were getting ready to order what may be the final revision of the S-100 Mini Front Panel Board (AKA FPMini).
I'd like to get an idea how many builders are interested in obtaining this board.
If your interested please email me your request with desired quantity.
I'm hoping to keep the board in the $25 range.
Special thanks to Rich and Josh (Crusty) for helping shake out this board.
-- Don Caprio ilv...@gmail.com
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Don Caprio cap...@uxpro.com
http://www.uxpro.com
(925) 240-UNIX
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