it's a very complex thing.
And obviously is not to be done in just one day.
An external circuit must be done.
The process is curious, an error at cpu makes the ROM dump. The process i mean, is to make a call on the last address of the ROM, and set a register to high, so the cpu runs over all addresses dumping the contents.
A demo circuit is provided, in where the COP420 content is dumped in external RAM, and later the proccess is to dump again that RAM with the needed content.
Keep in mind, this chip has not address lines as such. only data, so, to read, you need to either make a copy in a ram / rom the outside and then read with A0-ram A15 on a recorder, or make a circuit lines connecting the data to a PC parallel port and read in sync with the CPU speed.
In other words, a whole real magic of engineering, to "try" to read.
Otherwise, "could" be, using the basic of Newbrain, sending data requiring the chip to dump the ROM, even byte by byte, but is only a guess, and maybe it's not possible.
Last edited by rondc; 03/16/11 05:50 PM.