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Re: [N8VEM-S100:6497] Re: MiniFP build - data bus question

Guys,

I just confirmed that my board is behaving the same way
as described by Ian and Rich.

Data Bus LED's all ON while system is running. When I stop
and single step the Data LED's operate correctly. Examine
Next works and RUN returns system to normal running
system.

I need some time to look into these issues. Hope it turns out
to be simple things.


On 03/ 2/15 09:23 PM, Ian McLaughlin wrote:
Gentlemen,

I finally got my board into my Northstar Horizon for testing tonight.

I can confirm that I am seeing the same thing as described previously.  RUN/STOP appears to operate correctly.  RESET appears to operate correctly.  Single Step appears to operate correctly.  I think EXAMINE might be working (I can set an address, and EXAMINE and always get the same value).

I'm not so sure about EXAMINE NEXT - each press seems to cycle through 4 different addresses (non-sequential) then go back to the starting address.

DEPOSIT is definitely not working. I am unable to DEPOSIT a value into RAM.

My setup - Stock Northstar Horizon.  The Northstar CPU board has a front panel connector which I have connected to the FP mini.
Jumpers - all combinations have been attempted, and I'm unsure what the correct settings should be.

I can perform any debugging or testing if anyone can suggest what I should be looking for.  Otherwise, I will wait for others to see what they find out.

Ian

  
On Mar 2, 2015, at 7:40 AM, Don Caprio <ilv...@gmail.com> wrote:

Rich,

I'm having the same Examine problem with my board as well.
Josh had the last prototype working and all his  mods went to the
schematic.

I need to go back and review our emails and make sure all the
changes got made.



On 03/ 1/15 03:05 PM, Richard Cini wrote:
A quick follow-up. I did some probing of the LS123 one-shots and I discovered something interesting. Pin 12 (Q-prime) on both U17 and U20 are free-running. The other one shots seem to be triggering properly. I don’t see any immediate cause for this, so I swapped the chips but I get the same result. 

Rich

--
Rich Cini
Collector of Classic Computers
Build Master and lead engineer, Altair32 Emulator

From: Richard A Cini <rich...@verizon.net>
Date: Sunday, March 1, 2015 at 4:29 PM
To: S100-Post <n8vem...@googlegroups.com>
Subject: MiniFP build - data bus question

Guys —

I finished my MiniFP board this morning and I can’t seem to deposit to or read from memory using the EXAMINE toggle. The “next” part of the function works, so I can step among addresses but the data LEDs are all on all the time (unless I set JP5 SSW_DSBL jumper). However, if I use the SINGLE_STEP switch, the data bus LEDs appear to reflect memory contents.

The experimental system is very simple CompuPro RAM17 (64k), IMSAI 8080 board, and the front panel. Before I say that anything is wrong, can someone confirm the jumpers? I think only the MWRT should be jumpered. The RAM17 is an IEEE-696 board so as I do for my IMSAI, I’ve isolated pins 20/70 (UNPROT/PROT) on that board.

Chip-wise, I’ve used LS (including the LS123 as recommended in the Wiki) except the 7402. I don’t have any 7400’s in-stock so I’m using LS00 for now…don’t know if that’s part of the issue since those gates are used in the EXAMINE circuit. I replaced the 8212 just in case, but that had no effect. The data cable is fine.

Any help, even questions to get me thinking, would be appreciated. I feel I’m pretty close to a solution here.

Thanks!

Rich

--
Rich Cini
Collector of Classic Computers
Build Master and lead engineer, Altair32 Emulator
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