H8 8080A/Z80 64K RAM ORG0 BRD

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Mitchell Smith

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Jun 1, 2021, 11:05:53 PMJun 1
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I'm thinking about building the H8 8080A/Z80 64K RAM ORG0 board.

Does anyone have a PCB available for sale?

If not I may place an order with OurPCB.

Thanks!

Mitch

norberto.collado koyado.com

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Jun 2, 2021, 12:07:27 AMJun 2
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Yes, I do have some spares. 

You are looking for this one; correct?

H8 8080A/Z80 64K RAM ORG0 BRD . KiCad files, Gerber files, and Schematics. 8080A-64K-V1_3.rar - Gerber files


Thanks,
Norberto


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Subject: [sebhc] H8 8080A/Z80 64K RAM ORG0 BRD
 
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Mitchell Smith

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Jun 2, 2021, 1:23:41 AMJun 2
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Yes, that's the one.
Just to confirm, I have a regular H8 with the 8080 CPU. No modifications.

Also looking for an extender board if you have one of those available.

Thanks a bunch!
Mitch

Glenn Roberts

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Jun 2, 2021, 5:41:44 AMJun 2
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This is a nice board. I didn’t appreciate the value of the on-board battery backup until I started using this with the H-8-5 serial port and front panel load and dump functions. This lets you load programs into RAM at any location and run them from the front panel by setting the PC and hitting GO. No OS or boot process required. Let’s you load up multiple programs and quickly run them, e.g. for demo purposes and at computer fests.

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On Jun 2, 2021, at 1:23 AM, Mitchell Smith <kb3...@gmail.com> wrote:



Steven Feinsmith

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Jun 2, 2021, 8:46:02 AMJun 2
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It is difficult to build 8080 and Z80 due to timing issues. You can use 8085 instead of Z80. The Z80 has an entire 8080 function with little software modification. My experience that you can run 8080 on Z80. But you can't run the Z80 on 8080.


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Subject: Re: [sebhc] H8 8080A/Z80 64K RAM ORG0 BRD
 

norberto...@koyado.com

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Jun 2, 2021, 3:06:23 PMJun 2
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The beauty of this board is that it works with any H8 monitor and CPU’s (8080A, Z80). As I can select any memory region, it can be used to debug older memory boards. For example, I select the first 8K region for this board, skip another 8K region, and enabled the older memory boars above this region to debug it. Then I use the H8 front panel monitor to debug such older memory board.

 

This board works fine up to 10MHz.

 

Norberto

Mitchell Smith

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Jun 3, 2021, 1:35:03 AMJun 3
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I watched a couple youtube videos from Shadow Tron. He built one of these. I love the memory backup battery. Great feature.

norberto...@koyado.com

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Jun 3, 2021, 2:39:40 AMJun 3
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Shadow Tron documented this 8080A/Z80 64K board in detail. He created 6 chapters which I enjoyed watching a lot. I need to add a link to my website.

 

https://www.youtube.com/watch?v=xpvd9NF3iq0  - chapter 1.

 

On this board the team rally behind it and it is well documented. I thank everyone that helped.

 

Norberto

Mitchell Smith

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Jun 30, 2021, 4:02:15 PMJun 30
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Norberto,
I received the circuit board and built it in about 3 hours. What an amazing job you did with this!! Thanks so much! It was so much fun I could barely stop myself.
The board appears to be working perfectly. I've been running the memory test routines on both banks.

I am a little unclear on the use of some of the jumpers.
Could you clarify JP3 - “H8-SS (Side Select)”: Which one do I use? Pin #18 or #24? And why?
J1 - Side-Select.  If the A16SW switch controls the second memory bank then what is this jumper for?

I guess I just don't understand how J1, JP3 and JP4 work together.

Thanks again!
20210630_151120.jpg

norberto...@koyado.com

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Jul 1, 2021, 12:33:37 AMJul 1
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Great news! This board was designed to support the Heath Z80 and the Heath 8080A with any H8 monitors. Also it works with any other Non-Heath Z80 boards.

 

Which one do I use? Pin #18 or #24? And why? I decided to use pin#18 as it was Heath default to control the H17 floppy side sel signal. Heath gave the option to use pin#24 as well, but it was optional. The Z80 V4 uses pin#24 to send the IRQ signal to control better the I/O boards. It uses pin#18 by default to control H17 floppy side sel signal.

 

If the A16SW switch controls the second memory bank then what is this jumper for? You can add an external switch to toggle A16 manually. As it is battery backup to can use the upper 64K to store your own programs. Also if serves as a 64K spare region in case the first 64K goes bad for any reason.

 

J1, JP3 and JP4 work together.

 

JP1 – Install only when using NiCad rechargeable batteries. Do not install if using regular 2032 batteries

JP3 – Install jumper across pin 1-2 to select pin#18 on H8 bus as H17 side select (default).

JP4 – Install jumper or external switch to select either first 64K or second 64K. I usually install a jumper to store custom programs on the upper 64K region when using Heath CPU boards (memory test, front panel tests, H17 tests, etc.) I take out jumper to use the first 64KB region to boot HDOS or CP/M. Also it can be used as a spare 64K bank in case the first 64K bank goes bad.

JP5 – Install jumper across pin 1-2 when using Heath 8080A CPU. Note: The H8 “HA8-8 Extended Configuration” board must be removed. If using Z80’s with on-board Extended Configuration circuit, then a jumper must be added across pins 2-3 to disabled on board ORGSEL signal.

 

The maximum speed this board can do is 10MHz when using my Z80 boards. This board improves the reliability of the H8 system when using the 8080A board. Older memory boards have so many timing issues and it is a waste of time in fighting with them. I ran my H8 system for months non-stop while testing the CF storage solution and it never crashed.

 

Give me time on the H8 Extender as I need to improve its reliability. 😊

 

Thanks and have fun,

.

norberto...@koyado.com

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Jul 1, 2021, 12:47:04 AMJul 1
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I forgot J1.

 

J1 – Is a copy of “P1” from the original Heath “HA8-8 Extended Configuration” board.

 

This is in case pin#18 and pin#24 are used for other functionality, so that you can add a wire from here directly to the H17 controller to control floppy side select.

 

 

Norberto

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norberto...@koyado.com

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Jul 1, 2021, 2:10:01 AMJul 1
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I forgot J1.

 

J1 – Is a copy of “P1” from the original Heath “HA8-8 Extended Configuration” board.

 

This is in case pin#18 and pin#24 are used for other functionality, so that you can add a wire from here directly to the H17 controller to control floppy side select.

 

 


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Mitchell Smith

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Jul 1, 2021, 7:26:59 AMJul 1
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Thanks for clarifying that for me Norberto.

Now on to the next problem....
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