Cromemco SCC Eproms - test-drb@ccmp.vtda.org

22 Jan 2004

On Jan 21, 17:40, Joe Abbott wrote:

...
  Just my luck! Thanks anyway, Pete. Hopefully someone
 out there will be able to help. 
I hope so!

...
  I'd bet yours contains the code to disable the
onboard
 roms and jump to the floppy boot rom.  My System Zero
 manual mentions this and lists the asm code as well as
 a hardware mod.  Might be why there doesn't seem to be
 many of these roms around. 
Could be.  The first EPROM "lives" at 0000H so mine contains:

0000  3E 00        LD A, 0
0002  D3 23        OUT (23H), A    ; dunno what this port does
0004  3E 01        LD A, 1
0006  D3 22        OUT (22H), A    ; nor this one
0008  21 16 00     LD HL, 16H      ; 22
000B  11 00 24     LD DE, 2400H    ; 9216 or start of non-SCC memory
000E  01 07 00     LD BC, 7
0011  ED B0        LDIR            ; copy 7 bytes from 0016-001C to
2400
0013  C3 00 24     JP 2400H        ; and execute there
0016  3E 80        LD A, 80H       ; set top bit
0018  D3 2A        OUT (2AH), A    ; don't even know this one
001A  C3 00 C0     JP 0C000H       ; start of RDOS?

-- 
Pete						Peter Turnbull
						Network Manager
						University of York