Ok, thanks. I have been disassembling the ROM and learning Z80 assembler as I go as I spent all of my early days with 6502 assembler on Apple IIs and BBC Micros. When I switched to CP/M it was Pascal and C so I missed out Z80 assembler (apart from a space game on the ZX81, but I'll not count that). With that in mind and with a view to reducing the number of variables, do you have any suggestion as to what the code might be?
The memory map is divided into 8K blocks as follows;
Code:
0000 - 1FFF ROM
2000 - 3FFF VDU RAM
4000 - 5FFF CHAR GEN
6000 - 7FFF STATUS (RD)
8000 - 9FFF KEYBOARD
A000 - BFFF DATA PORT
C000 - DFFF STATUS (WR)
E000 - FFFF RAM
I guess reading or writing from/to each of the blocks would allow me to pop a logic probe on the various chip selects.
The basic issue is that I don't really know what I am doing
. One thing I am fairly certain of though is that, in this case at least, it isn't a faulty socket as there aren't any
.