[Coco] Kip's Single Board Computer

Darren A mechacoco at gmail.com
Tue Sep 8 23:38:13 EDT 2015


On Tue, Sep 8, 2015 at 9:27 PM, Dave Philipsen wrote:

> Actually, thinking about it, if it's a two-cycle instruction then the
> address would just increment once every two cycles.  The CPU only fetches
> one byte.  Two cycles later it fetches the next byte at an address that is
> just one greater than before. So you'd get address $1212 for the first NOP,
> $1213 for the second NOP, etc.  A0 would oscillate at 500 MHz for a 1 MHz
> clock, A1=250 MHz, etc.
>


Every cycle will be a byte fetch.  The first cycle of a NOP instruction is
the fetch of the NOP opcode. The second cycle is a fetch of the next
opcode.  The end-result is the same (the address increments every other
cycle).

- Darren


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