To implement PHX, you need the machine to do exactly the same as it does for PHA, but in the cycle that it presently reads A from the regfile it would need to read X.
Yes. In the first place, the opcode mask needs to include the new opcode here
Secondly, it needs an extra opcode mask to set src_reg to SEL_X register here
I think that should be it. Of course, with all opcode extensions you have to watch out that the new opcode doesn't overlap with a "don't care" in one of the existing patterns.
Probably worth a new thread: firstly because it might become quite long, secondly because that will keep all those messages conveniently in a single place, thirdly because those messages won't then interleave with any other discussions that might arise in this thread. It's a specific worked example...
Cheers
Ed
I'll start one in the Programmable logic section...
Arlet wrote:
BigEd wrote:
To implement PHX, you need the machine to do exactly the same as it does for PHA, but in the cycle that it presently reads A from the regfile it would need to read X.
Yes. In the first place, the opcode mask needs to include the new opcode here
Secondly, it needs an extra opcode mask to set src_reg to SEL_X register here
I think that should be it. Of course, with all opcode extensions you have to watch out that the new opcode doesn't overlap with a "don't care" in one of the existing patterns.
That's a great start and finish, heh. I was focusing on your second point. I would've missed the first point. I do plan to put the core through simulation, like we have in the past to make sure the new opcodes work as expected.
