They are there to precharge the bus - if it's charged to 1 then it's easy to arrange a conditional discharge to zero. An undriven node will act as a latch for free, at least for milliseconds, and that's easily long enough.


The whole concept of precharging might need a bit more explanation.

The ...

Okay, next thing:
The phi2 seems to be connected in the precharge mosfets, so I guess I could try to figure them out now.

I believe the precharge mosfets are used to "latch" the bus state. But how does it actually work? The mosfet shouldn't be active during phi1, but it still keeps the value in the ...

I'm afraid that visual6502 won't be useful for me any time soon. It's just hard to read and understanding what you are seeing will take some time to get used to.

Using the block diagram and this document , I think I have a pretty good understanding of how JSR operates.



1. Fetch opcode to IR and ...

What about interrupts signals? As far as I know interrupts wait for current instruction to finish with BRK begin only exception if it hasn't started storing anything to the stack yet. Interrupts should have fairly similar micro op structure to BRK, but do they have to use a cycle to detect the ...

I'm trying to make a 6502 emulator (mainly 2A03) that has the instruction decoding in it as well. For this reason I'm trying to understand the decoder to implement it correctly.
According to several sites the decoder is a 130x21 logic array. Where do these values come from?
According to one site the ...