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Old 6th May 2021, 8:50 pm   #9
Michael Haardt
Join Date: May 2021
Location: Titz, Germany.
Posts: 41
Default Re: New SC/MP II system

I tried 600 baud at 2 MHz and kitbug does not always recognize the CR to stop showing memory contents. It looks like it just samples sense-b, so that may fail at either speed, because lower speeds need more time to output characters.

I am aware of the relationship between clock and the speed constants in the code. It took me a while to figure that out and I checked the serial timing with a logic analyzer. The published table I found late is perfect for 1200 baud at 4 MHz. I used a crystal oscillator to avoid the slight frequency offset non-matched crystals have.

Today I stumbled upon a surprise: Is the SC/MP little or big endian? I don't see any 16 bit operations, so it may be neither, but the original SC/MP assembler stores word (.dbyte) in big endian. Is there a reason?

I found the link for at least one ESS record in my notes:

Regarding the Elektor RAMIO SC/MP board with LEDs and DIP switches: In 1983/1984 I made a PCB and built the same thing as my first computer, but being unable to obtain a SC/MP I used a Z80. That was fun indeed, but I never met anybody who knew that system.

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