🚀 go-pugleaf

Simon Jones (sim...@removethis.videologic.com) wrote:
: > I can still remember some of the opcodes... Lets see now...
: > 
: > C4 00 07 8F FF C4 01 07 8F FF 90 F4

: yes, very familiar, can't remember what 07 was though

07 = CAS (Copy Accumulator to Status)

: L1:	ldi 00
: 	xx
: 	dly ff
: 	ldi 01
: 	xx
: 	dly ff
: 	bra L1

: > Anyone know what it does?

: was it something like shift acc right into serial out pin?

That would probably have involved the extension register - an 8-bit 
register that you could shift right with the LSB falling out onto the 
SOUT pin of the CPU and the MSB being loaded from the SIN pin.

: so the code would generate a tone if you connected a speaker to it?
: I can't remember how long the delay instruction waited so maybe it 
: flashed an LED

You got it. Bit 0 of the status register was flag F0 which was brought 
out to a pin on the chip (so were Bits 1 and 2). I connected an LED 
there. From memory it had a frequency of the order of 1 Hz.

: Any chance of putting some of this information on the net ?, I've looked 
: but haven't found any detailed info on the instruction set or hardware.
: If I can get enough info on the MK14 (circuit diagrams anyone...?) then 

I still have my MK14 schematics (and of the cassette interface, but 
nothing more), and source listings of the original and revised monitor ROMs.

But what about copyright? I can't believe many people would care after 
over 20 years, but still. Who does own the MK14 ROM now?

: I'd quite like to have a go at writing an emulator for *total* 
: nostalgia..

: Simon

-tony