Help with H8-Z80-64 CPU/GIDE board...

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Joe Travis N6YPC

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Oct 21, 2022, 3:34:40 PM10/21/22
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  Greetings All,

I acquired an H8-Z80-64 CPU/GIDE board along with an H8 Speed Mod board from Norberto some time ago and finally decided to build and use them.  The CPU board had been assembled and partially populated when I received it (most of the ICs near the bus connector, the two 5V regulators, the two ROMs and the 2 MHz oscillator). 

I installed all the jumpers for my intended configuration (no H37, using a WH8-64K memory board, no GIDE).  The 2 MHz oscillator jumpers are as depicted in the photo of the Assembly, Configuration and Installation Guide  (Rev. 4, August 25th, 2017).  The board originally came with a 444-19 ROM installed at U3 but, after I realized it was incorrect, I liberated the only 444-70 ROM I have from my favorite H8.  I hope to burn an EPROM (to replace the ROM) and modify the board accordingly once I get it going.

When I power up, all I get from the H8 is: PWR, RUN, ION LEDs are ON, all others are off and the H8 speaker wails ("it's one long song").  Front panel reset clears the ION and speaker sometimes.

Photo attached.  Any help from those familiar with this board is greatly appreciated.  Thank you!

Regards,
Joe Travis n6ypc

20221021_145847.jpg

glenn.f...@gmail.com

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Oct 21, 2022, 5:26:51 PM10/21/22
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Joe: this is the same board I have in Rusty and I actually have a second one of these – both in operational condition. The Rev 2.6 board is the last iterative improvement that Norberto made of the original “Les Bird” Z80 board.  Subsequently Norberto incorporated the speed function and other capabilities directly on the CPU board (Revs 3.1 and up).

 

This configuration has run rock steady for me for a long time.

 

I took pictures of my second Rev 2.6 board, which is configured for stand alone operation.  The system has only the CPU board and the Speed board installed. Pix here:

 

CPU board: https://photos.app.goo.gl/VHhp7X131ZPuFkCt7

Speed board: https://photos.app.goo.gl/hUnBy8VJw29ePre96

 

I realize you’re trying to test the CPU board initially (without the speed board). I would recommend using header pins and shorting blocks on the “A B” configuration area for CPU speed.  I’m not sure how to configure those pins.  on my system nothing is connected there as the speed board does the work.  Les had some documentation on  how to set these in his original writeup: https://sebhc.github.io/sebhc/pcbs/H8-Z80-64_Rev2.pdf.  Again, when using the speed board I have no jumpers set there so I recommend headers/shorting blocks for configuring this part of the board.

 

One thing I notice is you don’t have a jumper on the 555 circuit. You have to pick whether you want the LM555 of Front Panel to do the reset function. I have mine set for “LM” (LM555).

 

On mine I do not have a jumper on the “X” jumper.

You also seem to have the jumper (bottom right) set for “H37” – that’ll definitely cause a problem. move that to the left two pins.

 

 

Try those changes and see what happens…

 

  • Glenn

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norberto.collado koyado.com

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Oct 21, 2022, 7:06:29 PM10/21/22
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Thank you, Glenn,☺️ for such detailed information to debug his board. ☺️☺️

From: se...@googlegroups.com <se...@googlegroups.com> on behalf of glenn.f...@gmail.com <glenn.f...@gmail.com>
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Subject: RE: [sebhc] Help with H8-Z80-64 CPU/GIDE board...
 

glenn.f...@gmail.com

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Oct 21, 2022, 7:58:38 PM10/21/22
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Joe: according to David Troendle’s writeup on the Z80 Rev2 board the A B jumpers you have are installed correctly for use with a 2 Mhz oscillator:

 

https://koyado.com/Heathkit/H8-Z80-64-V2_files/H8-Z80-64K%20Assembly%20Guide%20Rev%204.pdf (p. 15)

 

but you probably already knew that… 😊

 

I do believe you’ll have to remove those jumpers when you go to use the speed board…

 

 

 

From: se...@googlegroups.com <se...@googlegroups.com> On Behalf Of Joe Travis N6YPC
Sent: Friday, October 21, 2022 3:35 PM
To: SEBHC <se...@googlegroups.com>
Subject: [sebhc] Help with H8-Z80-64 CPU/GIDE board...

 

  Greetings All,

--

Joseph Travis

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Oct 21, 2022, 11:33:22 PM10/21/22
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Thank you all for your replies, unfortunately it's still a "work in progress".

Initially, I only had the REV. 4 documentation to go from.  I set all the jumpers according to what it said and didn't install any that weren't mentioned (such as LM which was so keenly recognized by some) . I was happy to receive the REV. 2 documentation (thank you) because it gave some fair explanations for many jumpers, not all.  However, some of the jumper settings are in conflict with those in the REV. 4 documentation.  In particular: X, U4, U3, H37 which just leads to more confusion because I don't have a schematic to see what it actually does.

About 15 minutes after I sent the email, it dawned on me that the WH8-64 has a jumper which must be set according to what CPU board is being used (8080 or Z80).  Both of my H8s use 8080 CPU boards.  If memory serves (pun intended) me correctly, it has to do with refresh.  A few hours later, after walking the dog, eating dinner, family stuff, I was able to get back to this and try it out along with all of your suggestions.

I can't tell if changing the jumpers at X, U4 and U3 really had any effect.  I ended up going with those recommended in the REV. 2 documentation.

Moving the jumper on the WH8-64 had the biggest effect as it began to show signs of life but, that was after I switched U3 from an original 444-70 ROM to an EPROM (from my test fixture CPU board).  The pinout is slightly different between the two.  The H8 is trying to work, it shows recognizable (not necessarily meaningful) stuff on the front panel which tells me the CPU is running but doesn't accept keyboard input.  The front panel reset works (sorta) sometimes.

I also noticed some "sensitivity" as to the CPU and memory board positioning.  Normally when I'm troubleshooting a system, I remove all unnecessary boards and space out the CPU and memory boards to give me room to probe around, etc.  In this case, the CPU board "doesn't like it" when the memory board is 2-3 slots away.  It prefers to have it close by.  If I were running at greater than 4 MHz, I might understand that however, I'm just trying to get it going at 2 MHz.

At this point, in addition to the above mentioned list, I have:
* Removed all ICs, inspected their pins and sockets, tested and verified each one before reinstalling them.
* Swapped the Z80A with a Z80H (keeping my hopes up)
* Ordered a AS6C1008 memory chip (although I'd still like to get it working with external memory)

Any other thoughts are greatly appreciated... I do have a couple questions:
1.  Has anyone used this CPU board successfully with an external memory board (i.e. WH8-64)?
2.  Norberto, do you know if this CPU board worked before I got it from you?

Thank you all once again for your kind attention and assistance!

Regards,
Joe Travis n6ypc







norberto.collado koyado.com

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Oct 22, 2022, 2:03:28 AM10/22/22
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Norberto, do you know if this CPU board worked before I got it from you?

 

Yes, it was functional before. I used it a lot.

 

Please send me the CPU board back to check it out. Also, I ordered some 8080A/Z80 RAM boards as I have several users asking for such board. Because of all the pain the Z80 is causing you, I will give you a RAM pcb board that can run at 10MHZ. You can put in any slot in the H8 chassis once assembled. Also, I will include the 8080A EEPROM adapter as well as I need you to verify its operation using the 8080A CPU board.

 

Thanks,

Norberto

glenn.f...@gmail.com

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Oct 22, 2022, 7:04:33 AM10/22/22
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Joe: a few more tips to possibly help get your board working:

 

  • The jumper configuration instructions refer to IC part numbers that unfortunately are hidden when the chips are installed. Attached is the Xray view for reference
  • I have attempted to replicate your configuration by installing a 2mhz oscillator and the two AB jumpers as you have done (no external speed board)
  • I did install the “X” jumper, per the instructions.  I can’t recall its function but these jumpers come from the original 8080 design as I recall?
  • I did not install the “A4, A5, A6” jumpers by U302. I believe these are for the GIDE circuit (?) which I did not implement.
  • I removed the on-board RAM chip and set the RAM configuration jumper for “BUSS”
  • I do not have a Heath 64K RAM board but I do have a modern 64K “Les Bird” SRAM board, which I used for testing
  • Here is a picture of my configuration:
  • https://photos.app.goo.gl/qXFrQmfeeKZACnb76

 

I have installed these two boards in an H8 chassis and they operate fine.  I suggest you exactly copy my jumper configuration and try it with your Heath 64K RAM board and see if that gets the board operational.

 

 

From: se...@googlegroups.com <se...@googlegroups.com> On Behalf Of Joseph Travis
Sent: Friday, October 21, 2022 11:33 PM
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Douglas Miller

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Oct 22, 2022, 7:18:03 AM10/22/22
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Just one note regarding the H8 bus and dynamic RAM refresh. The H8 bus carries none of the Z80 DRAM refresh signals, so external DRAM must always refresh itself (in contrast to, say, the H89 where the Z80 directly refreshes the DRAM). I'm not sure what the external RAM board jumper "z80" is for, but it would not be refresh as far as I can tell. SRAM, of course, does not require refresh.

Glenn Roberts

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Oct 22, 2022, 7:30:57 AM10/22/22
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Although I understand the desire to keep these systems as original and authentic as possible, the single biggest source of problems in debugging H8 systems (for me anyway) has been older memory boards, particularly DRAM-based ones. For any system that I want to be reliable I use a modern SRAM-based memory chip.

Sent from my iPad

On Oct 22, 2022, at 7:18 AM, Douglas Miller <durga...@gmail.com> wrote:



Les Bird

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Oct 22, 2022, 12:56:08 PM10/22/22
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Glenn, yes those jumpers on the right side of the board were taken from the 8080 CPU board. In fact, the entire right half of that card is from the 8080 schematic.

If I remember correctly I believe those jumpers allowed to configure for different types of ROMs.

Les


glenn.f...@gmail.com

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Oct 22, 2022, 9:16:07 PM10/22/22
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“X” is the ROM DISABLE jumper. Per the Rev. 3.1 board instructions: “When jumper inserted drives /ROM_Disable signal into the H8 bus” … “not inserted” for normal operation.  I do not have the “X” jumper installed on any of my newer Z80 boards (2.6, 3.1, 4.0) and they operate fine under HDOS and CP/M, CP/M3, etc.

 

So there does seem to be a conflict in the instructions between the 2.6 (p. 14, step 7.2) and later boards.  For just seeing if the board comes up at power-on either position seems to work.

 

On the 8080 when you upgrade to the HA-8-8 “extended configuration” (ORG zero) board the instructions say to insert the “X” jumper…

Joseph Travis

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Oct 24, 2022, 9:19:20 AM10/24/22
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'Sorry to have kept you all in suspense... I tried each and every suggestion but could not get this Z80 CPU board to work with the WH8-64.  BTW - The previously mentioned 8080-Z80 jumper on that board is for READ timing, nothing to do with refresh.

I (along with many of you) came to suspect it may / is a timing issue.  I was waiting for the arrival of the AS6C1008 RAM chip (due here today or tomorrow) to verify my suspicions but woke up in the middle of the night thinking "I've got 3 H8-1 8K Static Memory boards... I wonder if they will work?"  When I awoke this morning, I went downstairs to the "Service Department" and tried them out.  Attached is a photo of my test fixture running the memory test.

'Mixed emotions... I'm happy it is working, I'm sad it's not with the WH8-64.  I'm happy it's working!

Thank you all so much for your kind assistance!

Regards,
Joe Travis n6ypc


20221024_085516.jpg

norberto.collado koyado.com

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Oct 24, 2022, 10:06:52 AM10/24/22
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Great news!

 

I will send you a pcb 64K board by weekend as your WH8-64KB board is kind of non-operational with the Z80. It must be a timing issue on such board.

 

Thanks,

Norberto

Glenn Roberts

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Oct 24, 2022, 10:57:28 AM10/24/22
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Great outcome Joe. You’re undoubtedly tired of hearing it from me but the first thing I suspect in cases like this is the DRAM board - encountered this many times. Glad you’re up and running.


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On Oct 24, 2022, at 10:06 AM, norberto.collado koyado.com <norberto...@koyado.com> wrote:



Joseph Travis

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Oct 24, 2022, 11:48:44 AM10/24/22
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Norberto,

There's no need for you to send me a memory board.  The WH8-64 works fine with my 8080 CPU Board and I'm expecting to receive an AS6C1008 RAM for the Z80 CPU board today or tomorrow.  Thank you!

BR,
Joe


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Joseph Travis

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Oct 24, 2022, 11:51:10 AM10/24/22
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I never grow tired of you Glenn!  Although, I had wondered at times if you grow tired of me...  Thanks Bud!

BR,
Joe


Glenn Roberts

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Oct 24, 2022, 12:15:13 PM10/24/22
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Joe: will you end up with two systems then when all is done? Do you have a second H8 chassis? Or will you swap boards ?

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On Oct 24, 2022, at 11:51 AM, Joseph Travis <jtravi...@gmail.com> wrote:



Joseph Travis

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Oct 24, 2022, 1:49:59 PM10/24/22
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I've got two working systems at the moment.  My "favorite" which is upstairs with the H11 and my "test fixture" which is downstairs in the "Service Department".  The test fixture is where I'll test all my boards (old or new) and run "experiments".  I had planned multiple roles for the H8-Z80-GIDE and I'm glad we discovered the issue with the WH8-64 board (and probably other DRAM boards) as this would have caused me a lot of grief had I used it to troubleshoot those memory boards.

Joe


Joseph Travis

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Oct 24, 2022, 5:45:56 PM10/24/22
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I received the RAM chip from Digi-Key this afternoon, plugged it in and changed the memory jumper accordingly... works great!

Thanks again everyone for your help!

Joe

norberto.collado koyado.com

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Oct 24, 2022, 6:30:04 PM10/24/22
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You get the best performance out of the Z80 CPU when using the on-board RAM. It allows to clock it up to 10MHz if needed. Also, you free up a slot on the H8 backplane.

Glad to know that it is working fine.

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glenn.f...@gmail.com

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Oct 24, 2022, 7:48:50 PM10/24/22
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Awesome outcome Joe!

 

Next you should be able to try out the speed board!  Documentation and speed utility are on Norberto’s site

https://koyado.com/Heathkit/H-8_Speed_Mod.html

 

but you can also use the front panel to change the CPU speed.  Output 0, 1, 2 or 3 to port 220Q to set the speed per the following table:

 

 

 

If you haven’t modified the front panel the display LEDs won’t refresh properly at higher speeds (though the OS should work fine).  My preferred solution is to put a 2.048 Mhz oscillator right on the FP board.  I documented this a while back with some pictures:

https://photos.app.goo.gl/Pqv585iafF2jFsCF7

 

but there were also other workarounds (I think this is discussed on Norberto’s site).

 

If you have the new front panel from Norberto this already has the fix built in…

 

Let us know when you’re flying at 10 (or 16?) Mhz!

 

  • Glenn
image001.png

norberto.collado koyado.com

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Oct 25, 2022, 6:10:26 PM10/25/22
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Use this file to test with the front panel. It uses port 362Q, same as the H89 and on Z80 V3&V4.


Thanks,
Norberto

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Joseph Travis

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Oct 25, 2022, 7:16:08 PM10/25/22
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Thanks Norberto.  That is essentially how I tested it although I didn't know that file existed.

Joe

glenn.f...@gmail.com

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Oct 25, 2022, 7:34:16 PM10/25/22
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Thanks. Obviously more current than my older information.

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