[Coco] Desired RESET behavior

[Theodore (Alex) Evans]

On 01/29/2016 10:27 PM, RETRO Innovations wrote:
> I was able to speed up the SPI by using the awesome quadrature clocks of
> the 6809.
>
> q ^ e generates a doublespeed clock, which means the SPI will operate at
> 2X the normal clock.  Thus, a byte can be transferred in 4 E clock
> periods.  I am not as familiar with the 6809 opcode timings, but I would
> assume that most opcodes that can read/write $ffXX would take at least 4
> clock periods.  Are there any that do not?

Clock periods from when?  If you are talking about from the time the 
address is asserted on the address bus. All of them do.  If you are 
talking the time from one read to another, you can read into A or B in 4 
cycles (or 3 on the 6309) (LDA <$XX and LDB <$XX) and D, U, or X in 5 
cycles but this reads two successive bytes (LDD <$XX).  If you are using 
a 6309 there are instructions which can read from memory (as data) every 
other cycle while simultaneously writing every other cycle.