[Coco] Kip's Single Board Computer

[Dave Philipsen]

Thanks for the clarification!


On , Darren A wrote:
> 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