| Posted By
vigsa (HUN)
on 2008-12-27
13:33:04
|  Using a 50% functional Plus4
Hi, my plus/4 doesn't functioning well (See the topic: MISSING BASIC???), but it can load programs from tape. (Machine code: L "",1) It looks like everything is loaded, but I cannot start the program. The Turbo says: press F3 to start. F3 is programmed to: SYS 4100, but my BASIC doesn't functioning. I tried to start the program with: Runstop+reset then G 1004. (I assume that SYS 4100 = G 1004) but nothing happens. I've found some code in the memory, but I cannot find the real starting point. Does anybody have an idea? Please help.
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Posted By
vigsa (HUN)
on 2008-12-27
14:19:14
| Re: Using a 50% functional Plus4 - part II
Question #2: Where does BASIC store the program? (fe.: 10 SYS 4100) Where can I find it? I used the H (hunt) command, but I didn't find anything.
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Posted By
SVS
on 2008-12-28
04:00:02
 | Re: Using a 50% functional Plus4
Assuming that the uP is good, try this:
MONITOR
M 8000
>7F8 80
M 8000
if the result is the same (or alike) system is not able to switch from ROM and RAM banking. Since the monitor commands seem to work, the problem could affect the TED too. Have you tried to pull the TED chip and to re-push inside the sock?
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Posted By
Csabo
on 2008-12-28
09:33:34
| Re: Using a 50% functional Plus4
Answer for #2: by default, BASIC programs start from $1001. However, this can be easily changed by adjusting the bytes at $2B/2C. To find out where the current BASIC programs is, go to monitor and type >2B. Example: let's say it displays: >002B 01 40 .. .. .., then your BASIC program is at $4001.
That's it specifically for BASIC programs, but reading your two questions again I think this may not be what you're looking for. I think you want to know the starting address of a machine language program. That's not as trivial as with BASIC programs. You could look for the usual places (around the $1000 area), try H 1000 FD00 78 8D 3F FF (which is SEI, STA $FF3F, a somewhat common start), or just ask us specifically which program it is 
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Posted By
vigsa (HUN)
on 2008-12-28
19:34:53
| Re: Using a 50% functional Plus4
First: thanx for the tipps.
info: I have removed all the chips, cleaned everthing and put it back. It doesn't solved the problem. 
I'll try the >7f8 80 trick tomorrow, and I'll will update you
That's what I do nowdays: I got more then 80 tapes. Yes, tapes. I start my plus4 in Tedmon. L "",1 Press play on tape... the program loads (4 of 5 still loadable...) Runstop + reset. M 576 (where F3 text is...) looking for SYS XXXXX. When I got it, I convert it to hex and start with G YYYY. When the program starts with RUN, than I look for: M 1000. In most cases I find a SYS call there. Unfortunately sometimes there is a small basic code, then I have to skip that program. Additionaly I log everything in excell (in my laptop)
So, I'm a kind of busy nowdays.
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Posted By
Rachy
on 2008-12-29
03:31:12
| Re: Using a 50% functional Plus4
I meant: remove the 3-plus-1 chip permanently.
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