[Coco] Multi Pack Replacement

[RETRO Innovations]

On 2/23/2015 11:10 AM, S Klammer wrote:
> You may have condidered this, but, could something like I2C be used to send
> some signals to the 2nd pcb?
I thought of that, or just a simplistic parallel to serial to parall 
shifter.  But, there's at least 30 signals that need to be sent 
serially, and need to be done during a Q/E cycle, so that's 60MHz, far 
beyond I2C speeds.  And, I think you need to wait until mid through the 
first half of the E low portion to get stable signals, so that's 120Mhz 
(roughly).

Say 100MHz for calcs.

That's a 10nS clock, not sure how much TTL would work at 100Mhz (Maybe 
ACT logic or LVC or LXC family).  By the time you get done synthesizing 
a clock and synchronizing it to the 6809 clock, the silicon needed far 
exceeds the value to be gained.

Jim