Front Panels - Thoughts
rodsmallwood52 at btinternet.com
Sun Nov 1 10:31:32 CST 2015
Hang on that sounds familiar.
I worked at a company that sold Intel Development systems.
That sounds like one of them
On 01/11/15 14:18, tony duell wrote:
>> One problem with a front panel on an S100 machine - or any microprocessor-based
>> machine - is getting access to the program counter so you can tell it to start running
>> at some arbitrary address. The Altair/IMSAI panels resolved this with a hack, jamming
>> a jump instruction into the processor data lines (not the S100 bus data lines) via a
>> special connector to a special processor card.
> Although not S100, the Intellec MCS8i was a 8080 machine with a front panel. There was
> no hardware way to start the processor at a particular address (No logic to jam a jump
> instruction onto the data bus, for example). You did have a reset switch. So what you did
> was take the bus over from the processor (thus effectively halting the latter), toggle a
> jump instruction with the appropriate address into the first 3 bytes of RAM, then reset, and
> give the bus back to the processor. That was even the way to start the ROM monitor program
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