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SDC_85 - a tiny 80C85-based computer [message #5884] Tue, 29 January 2019 00:15 Go to next message
gbm is currently offline  gbm
Messages: 19
Registered: January 2018
Junior Member
It's time to present my newest child, probably the smallest 8085-based computer ever made (real, not FPGA):

SDC_85
- a tiny 80C85-based computer by gbm

Features:
• footprint: 80C85 DIL40 socket (width: + 50 mils)
• hardware monitor with single-stepping, disassembly, memory editing and drag-and-drop HEX file loading
• 32 KiB RAM, 64 KiB ISP Flash
• terminal (console) interface with interrupt capability
• timer with interrupt and single LED controlled via an output port
• SOD output connected to a LED, SID input controlled by a button or monitor command
• Power supply, h/w monitor communication and target computer terminal via USB double VCOM device
• whole computer logic implemented in STM32L412C microcontroller placed under the CPU

Software needed on PC side: a terminal emulator program (TeraTerm 4.101 or newer is recommended).

As all the machines from SDC line, the toy is designed mainly for presenting the details of CPU operation. It allows for instruction- and bus cycle-based single stepping to show the details of instruction execution and interrupt processing.
Top view:
index.php?t=getfile&id=1239&private=0
Bottom view:
index.php?t=getfile&id=1240&private=0
Hardware monitor console showing TinyBASIC startup code:
index.php?t=getfile&id=1241&private=0

[Updated on: Tue, 29 January 2019 00:18]

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Re: SDC_85 - a tiny 80C85-based computer [message #5885 is a reply to message #5884] Tue, 29 January 2019 00:33 Go to previous messageGo to next message
just4fun is currently offline  just4fun
Messages: 126
Registered: May 2017
Location: Dark side of the Moon
Senior Member
Hi,
very interesting!

Just a curiosity... there is any particular reason to use a "pricey" STM32L412C (and is is a little "monster"...) instead of a more cheaper (and more easy to find) STM32F103...?

Regards.
J4F
Re: SDC_85 - a tiny 80C85-based computer [message #5886 is a reply to message #5884] Tue, 29 January 2019 00:42 Go to previous messageGo to next message
pbirkel is currently offline  pbirkel
Messages: 60
Registered: October 2015
Member
gbm wrote on Tue, 29 January 2019 00:15
It's time to present my newest child, probably the smallest 8085-based computer ever made (real, not FPGA):

SDC_85
- a tiny 80C85-based computer by gbm

Features:
• footprint: 80C85 DIL40 socket (width: + 50 mils)
• hardware monitor with single-stepping, disassembly, memory editing and drag-and-drop HEX file loading
• 32 KiB RAM, 64 KiB ISP Flash
• terminal (console) interface with interrupt capability
• timer with interrupt and single LED controlled via an output port
• SOD output connected to a LED, SID input controlled by a button or monitor command
• Power supply, h/w monitor communication and target computer terminal via USB double VCOM device
• whole computer logic implemented in STM32L412C microcontroller placed under the CPU

Software needed on PC side: a terminal emulator program (TeraTerm 4.101 or newer is recommended).

As all the machines from SDC line, ...


Marvelous! When will it be shipping :-}?

And where can I find out more about "the SDC line"?
Re: SDC_85 - a tiny 80C85-based computer [message #5887 is a reply to message #5886] Tue, 29 January 2019 01:01 Go to previous messageGo to next message
gbm is currently offline  gbm
Messages: 19
Registered: January 2018
Junior Member
just4fun: L4 series is much more flexible than any F-series, and F103 is simply outdated (but soooo cheap - I used Bluepills for my other design, SDC_Zero). L412 is the cheapest model in L4 series, with 40 KiB RAM and some other nice stuff, like crystal-less USB - quite useful for tiny boards.

pbirkel: more on SDC varieties in this forum and 6502.org. Actually I have 9 more boards waiting to be assembled, just need to buy more L412. I can share the PCB designs of SDC machines as well as firmware binaries (sources - maybe some time later).

SDC_85 may run whatever fits into its Flash and RAM. TinyBASIC is just an example. Basically you load a .hex file into RAM, then you may burn it into Flash using a monitor command. During startup, lower 32 KiB are copied from Flash to RAM, RAM is mapped at 0 and the 2nd half of Flash at 32 KiB. It's possible to program the upper 32 KiB of Flash using RAM content.
Re: SDC_85 - a tiny 80C85-based computer [message #5889 is a reply to message #5887] Wed, 30 January 2019 10:17 Go to previous message
Sergey is currently offline  Sergey
Messages: 172
Registered: October 2015
Location: Portland, OR
Senior Member
That is a pretty cool, and really small 80C85 computer.
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