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MiniMax8085 - Extension Board [message #9184] Fri, 08 October 2021 14:23 Go to next message
Sergey is currently offline  Sergey
Messages: 236
Registered: October 2015
Location: Portland, OR
Senior Member
Hi,

I am designing an extension board for my MiniMax8085 SBC (https://github.com/skiselev/minimax8085Wink
It is rather a mix of components, that hopefully will allow to run a bit more things than just the monitor and the BASIC interpreter:
- 8231A/Am9511A floating point coprocessor
- 8254 timer
- 8255 parallel port interface
- Additional 32 KiB SRAM, which can be switched in instead of the ROM

The preliminary schematic and the PCB layout are attached.

I'd appreciate your feedback!

Thanks,
Sergey
Re: MiniMax8085 - Extension Board [message #9185 is a reply to message #9184] Fri, 08 October 2021 20:25 Go to previous messageGo to next message
b1ackmai1er is currently offline  b1ackmai1er
Messages: 396
Registered: November 2017
Senior Member
Nice, love to build one.

Re: MiniMax8085 - Extension Board [message #9188 is a reply to message #9184] Sat, 09 October 2021 13:39 Go to previous messageGo to next message
alkmar is currently offline  alkmar
Messages: 29
Registered: August 2019
Junior Member
I can't wait until you sell PCB's or release the gubers I have two MiniMax8085 who need a friend Razz
Re: MiniMax8085 - Extension Board [message #9234 is a reply to message #9184] Mon, 18 October 2021 13:16 Go to previous messageGo to next message
Sergey is currently offline  Sergey
Messages: 236
Registered: October 2015
Location: Portland, OR
Senior Member
PCBs ordered, I'll keep you updated on the testing progress.
I'll post the design on GitHub once it is tested
Re: MiniMax8085 - Extension Board [message #9593 is a reply to message #9234] Sat, 08 January 2022 00:19 Go to previous messageGo to next message
Sergey is currently offline  Sergey
Messages: 236
Registered: October 2015
Location: Portland, OR
Senior Member
Well, it's been a while.
I made a stupid mistake in the first revision - used wrong footprint for DC-DC converter. Updated/reordered PCBs.
Spent some time building and testing the board over new year's break.
All seems to work properly. The only minor annoyance is that Am9511A APU's END signal is connected to TRAP, so it causes a non-maskable interrupt on completion of every instruction.
Anyway, as promised the design is here: https://github.com/skiselev/minimax8085-apu-ext

I have a few extra PCBs in case someone is interested. Probably just for the price of shipping...

/forum/index.php?t=getfile&id=2605&private=0
Re: MiniMax8085 - Extension Board [message #9605 is a reply to message #9593] Fri, 14 January 2022 14:12 Go to previous messageGo to next message
Sergey is currently offline  Sergey
Messages: 236
Registered: October 2015
Location: Portland, OR
Senior Member
b1ackmai1er, alkmar: Please let me know if you'd like the PCBs Smile
Re: MiniMax8085 - Extension Board [message #9627 is a reply to message #9605] Mon, 17 January 2022 13:30 Go to previous messageGo to next message
alkmar is currently offline  alkmar
Messages: 29
Registered: August 2019
Junior Member
Sent PM, I would love to get a pair of these PCB's Cool
Re: MiniMax8085 - Extension Board [message #9661 is a reply to message #9627] Sun, 23 January 2022 09:47 Go to previous messageGo to next message
alank2 is currently offline  alank2
Messages: 31
Registered: March 2019
Member
Sergey - are you planning on making a CP/M that can run on the minimax8085 using this extension board?
Re: MiniMax8085 - Extension Board [message #9681 is a reply to message #9661] Wed, 26 January 2022 08:05 Go to previous message
Sergey is currently offline  Sergey
Messages: 236
Registered: October 2015
Location: Portland, OR
Senior Member
Alank2, that was the idea... When I get some free time.
Unless someone else wants to take a stab at it.
It shouldn't be too difficult. One possible issue is the lack of storage devices, which can be resolved by using the PPI serial port to attach one (e.g. PPIDE).
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