[Coco] Kip's Single Board Computer

[Darren A]

On Tue, Sep 8, 2015 at 6:34 PM, Dave Philipsen wrote:

> Since NOP is a single byte opcode and a single cycle instruction the CPU
> will just move on to fetch the next instruction at an address one greater
> than the previous.  Again, it will find 0x12 there and thus execute a NOP.
> Since the CPU is stepping through addresses one at a time because of the
> fact that the NOP is a single byte instruction you will see very regular
> patterns when you view the address lines on a 'scope.
>


This is correct except that NOP is actually a 2-cycle instruction.  The 2nd
cycle of each NOP will read the following location.  The sequence of
addresses presented will be $1212 and $1213 for the first NOP, then $1213
and $1214 for the second NOP, etc..  So, following the first NOP, the
address bus will increment on every other CPU cycle.

- Darren