Re: Instruction decoder 6502

From: Sam Laur (
Date: 1999-02-15 09:39:50

> Total of 13 inputs. You could think of a 2764-EPROM but they have one 
> disadvantage: SLOOOOOOOOOW. 

There are some "fast" EPROMs (in the range of 50ns) but will they be fast
enough? Of course after that there's bipolar PROM but they tend to be small
and expensive.

> The last thing I am thinking of is to calculate all the equations and build the 
> decoder completely out of gates and decoders.

It would be interesting to do this, to see if one can make the "don't care"
terms match the ones in the original 6502 core (all the undocumented 
instructions :))

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