Re: Software 6502-on-6502, decoding address
Date: 2002-10-01 21:35:35

>> through
>> my head about a software 6502-on-6502 emulator (i.e., an emulator 
>> 6502
>> assembly that emulates a 6502). While this might seem like an
I've thought about that too; I think it would be quite useful for debugging, and also ripping, because a freezer can't get the complete state of a machine, but a simulator could.  Of course if the debugger in vice progresses you could at least do it on a big computer.  As for ripping; you could take the writes to SID area to rip any tune, if you could write a smart enough compressor that recognizes ARPs and such, it could also be quite compact data.
Thanks for the comments on solenoid, makes sense I never thought of that.

A question: how would one construct a circuit to toggle an LED everytime
$dfdf was accessed?
Ok, strange choice of location but I must admit, I first constructed a df decoder before remembering about the I/O2 line :)
Still, it's valid to ask how to decode an arbitrary address.  Not knowing any better I managed to do it with 2x3NAND
3xAND (5410, 7404, 5400):

Y1=(a15 AND a14 AND a12)
Y2=(a11 AND a10 AND a9)
Y4=NOT(a8) if J1 on 1-2, Y4=a8 if J1 on 2-3 (selects de or df)

Z3=(y3 AND y4)

X1=(z1 AND z2)

W1=(x1 AND z3)=true when (de,df) is present, else false

another question: is there a quick way to decode a large amount of zeros like "000000" or so.  And is there a  device with 2x8 sets of inputs, 1 output, that's like an 8bit address decoder, the address (high,low) byte would be on first set of inputs, and the fixed address using jumpers would be on the 2nd set of inputs, and the output would be low when the sets matched.  Would be ideal.
Only need 20 pins.

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