Reading RAM locations

[Roger Heflin]

On Mon, 14 Sep 1998, Ian Jones wrote:

> 
> We supply real time emulators that have the capability to display RAM data
> as long as the information is output to the address/data bus. Unfortunately
> this is not a cheap solution.
> 
> With regard to Roger Heflins idea of using a PC I/O card. I cannot see this
> working as a PC would not be fast enough to grab the data from a memory
> cycle.
> 
> 
> Ian Jones
> 
> tech at cobi.demon.co.uk
> 
> www.cobi.demon.co.uk
> 

Well, I think most of the snoopers generally also put the cpu into single
step mode.  That is if the CPU will run from DC->2Mhz (or whatever its
max speed is).   I think they control thing in single step mode by generating
the clock pulse itself and disconnecting the one on the chip.  On some 
cpus there may also be another pin that can be used to stop the cpu, using
this sort of thing you could use a pc i/o card.  Without this you would
need a special pc I/o card that could work at a higher rate, and whcih would
probably cost quite a bit.  This of course would not be a real time 
emulator as you make, it would be a snooper, and should be dooable for
quite a  bit less.

				Roger