Re: [EE] New retro-computing project

Em 10/03/2026 19:42, Harold Hallikainen escreveu:
> Thanks! I wire wrapped something like that using the MC6802 in the late
> 1970s. I remember how clever byte wide RAM and EPROM were. The pin outs of
> EPROM and RAM were the same except for a few pins. Various sizes of RAM
> and EPROM  also had the same pinout except for a few pins. Jumpers
> selected the type and size of memory. There was also byte wide EEPROM in
> the 28 series (as opposed to 27 for EPROM). In my wire wrapped board, I
> used a separate UART, a 65 something or another. Your board has the UART
> in the CPU. The MC6802 has the full 16 bit address on the pins, while this
> chip uses Address Latch Enable to multiplex the address onto the 8 bit
> data bus. As I recall, that's also what the 8088 did, as opposed to the
> 8086. But, it's been a while. I did have to deal with ALE on a Z80
> project.

I started with electronics in 1982, as a pre-teenager. Only discrete 
components soldered to phenolic linear terminal strips.

Soon I asked my mom to buy a PCB manufacture kit, by mail order, because 
we lived in a town really far away from the big centers.

Then I could

By 1984 I was starting with microcomputers (not mine), and finally by 
1986 (by miracle) I got a brand new MSX computer, an Sharp-Epcom Hotbit 
HB-8000. No disk drive, just tape recorder, and no monitor, just the 
home TV (when mom and dad weren't watching, i.e. by late night)


> One thing I really like about microcontrollers is that the address and
> data buses stay inside the chip. With systems with external memory and
> I/O, it is a real pain to find a problem when it affects one of the buses
> since NOTHING works. With microcontrollers, I can put in a power on self
> test that tests all the external devices and lets me know they are
> working.

But this microcontroller specifically doesn't have internal program 
memory, it needs an external EPROM.

So the problem is the same. One could use an 87C52 in place of the 
80C32. The 87C52 has 8 kiB de EPROM internally.


> The MC6802 wire wrapped board turned into a couple products. The schematic
> of one is at
> https://bh.hallikainen.org/uploads/HaroldHallikainen/20130416125553.pdf .
> This was designed with Dasoft schematic capture and PCB layout software
> running on a Cromemco CP/M computer. Long time ago!

I graduated in Computer Science in 1992, and in 1994 I started teaching 
at the Escola Técnica Federal de Goiás (now IFG). Then I was able to 
create more advanced circuits because the institution had electronics 
courses with several very capable teachers and good laboratories. There 
I created my first MCU boards. Before that I only used ready-made CPUs 
and computers and at most created circuits to connect to them.

Soon I started using Atmel 8051 MCUs (with internal EEPROM) and PIC MCUs.

We had to import most of the advanced parts by international mail order, 
from JDR Microdevices. I still have some of their prototype boards 
sealed in the bag.

When we learned about Mouser it was a delight. Although it was very 
expensive to buy parts this way, but it was the only way we could have 
modern (at that time) components.

Cheers,

Isaac

> Harold
> https://w6iwi.org
>
>
> On Tue, March 10, 2026 2:49 pm, Isaac Marino Bavaresco wrote:
>> PDF schematics available.
>>
>>
>> A textual description will take some time.
>>
>>
>>
>> Cheers,
>>
>>
>> Isaac
>>
>>
>>
>> Em 10/03/2026 17:48, Harold Hallikainen escreveu:
>>
>>> Interesting! Do you have more of a description and a pdf schematic?
>>> Grabcad is pretty nice! I have done schematic and PCB layout with KiCAD
>>> but have not tried the 3D modeling.
>>>
>>> Harold
>>>
>>>
>>>
>>> On Tue, March 10, 2026 12:29 pm, Isaac Marino Bavaresco wrote:
>>>
>>>> Hi All,
>>>>
>>>>
>>>>
>>>>
>>>> I just published on GitHub the design of an 80C32 board that I
>>>> designed last year.
>>>>
>>>> It's a project just for fun and to remember the old times, but it
>>>> might interest someone.
>>>>
>>>> <https://github.com/Ibavaresco/80C32>
>>>>
>>>>
>>>>
>>>>
>>>> Cheers,
>>>>
>>>>
>>>>
>>>> Isaac
>>>>
>>>>
>>>>
>>>>
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>

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