On 10/31/16 11:55 PM, Baltissen, GJPAA (Ruud) wrote: > So, Mike, how did you find out that it was 37000? If you look at the BIN > and see that the first bytes are a copyright text, It is obvious to start > with the code behind that text. But 37000? I just hope there is a trick > involved we all can learn from. I disassembled the ROM using da65. Its output includes labels for locations accessed by the code. I looked for familiar addresses. There was a label for $70, which is the CHRGET routine in RAM. BASIC wedges patch this routine, so I knew the ROM was some kind of wedge. I looked for where the ROM writes to $70+ to install its CHRGET patch. I found it at $9088 and below it at $9094 was the code to print the banner. $9088 makes the nice decimal number in SYS 37000 so I figured that was it. The MONJANA/1 ROM uses a similarly nice number; it starts with SYS 38000. >> but requires BASIC 2 (won't work on BASIC 4). > > I assume you found this out by putting the ROM in a 8032 as well? I tried SYS 37000 on a 2001 with BASIC 2 and it worked. I then tried it on an 8032 and it crashed. Since the 8032 has BASIC 4, I thought it might be a difference between BASIC 2 and 4. I went back to the disassembly and looked for calls into the BASIC ROM area. I looked up a few of them in "Programming the PET/CBM" by Raeto West. That book has a map of BASIC routines and their addresses in BASIC 1, 2, and 4. One of the calls was to $C9E2, which only works on BASIC 2. Regards, Mike -- Mike Naberezny (firstname.lastname@example.org) http://6502.org Message was sent through the cbm-hackers mailing listReceived on 2016-11-02 19:00:02
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