Date : Tue, 02 Feb 1988 14:14:00 PST
From : Alan Bomberger <ACB.COR@OFFICE-1.ARPA>
Subject: BIOS debugging
The way I always did this was to gen the test verision for 32K. Now Use the
DDT comand in you 64K version to BOOT the 32k version (This is done by changing
your disk and then using DDT to branch to the BOOT part of your ROM) It has
been so long that I can't remember how you arrange to regain control to the DDT
in high memory. Anyway the DDT in high memory uses the 64K version of the BDOS
to do its I/O, and the CCP, etc that runs in the 32K version is using the 32K
BDOS. No problem. One way to gain control is to Note the address in
location 38 (the DDT trap address) in the 64k version. load up DDT on the 32 K
version and change location 38 to point to the 64K value. Now the next
Breakpoint will cause control to pass to the DDT in high memory. Peace