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Apple-1-Integer-BASIC
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@ -138,6 +138,69 @@ Things seemed to almost work and then I powered the system off for lunch. After
Although it didn't get me closer to really having Integer BASIC running on the PAL-1, it did make me feel better to understand what had gone wrong.
## Honey I Broke the Assembler
I have used 64TASS as my assembler for 6502 work for years and been very, very happy with it.
After some tweaks to the code, I had A1B to the point where I could type and even run a program--but the listing was always garbled. I spent an entire weekend going through the code of the LIST portion of A1B looking for what might be broke. Several times I restarted tinkering with the code from scratch to make sure it wasn't something I was doing.
I always troubleshoot from the assembler list file... Except this time.
Because I was adding a lot of comments to the code as I would try to decipher what lines and segments of code did, I was looking at the source file.
Finally, in frustration, I decided I would compare the code byte by byte with a hex dump of the ROM. My assumption was that I was messing something up--maybe forcing the wrong address mode or something of that sort.
A quick scan of the assembler output listing stopped me in my tracks. Here is what jumped out at me:
```
.842b dd 00 02 CMP buffer,X
.842e b0 fa BCS Le42a
.8430 b1 fe LDA (synpag),Y
.8432 29 3f AND #$3F
.8434 4a LSR
.8435 d0 b6 BNE Le3ed
.8437 bd 00 02 LDA buffer,X
.843a b0 06 BCS Le442
.81
.844d 29 80 AND #$80
.844f c9 20 CMP #$20
.8451 f0 7a BEQ Le4cd
.8453 b5 a8 LDA txtndxstk,X
.8455 85 c8 STA text_index
.8457 b5 d1 LDA tokndxstk,X
```
Lookin at the source, I couldn't see anything wrong:
```
CMP buffer,X
BCS Le42a
LDA (synpag),Y
AND #$3F
LSR
BNE Le3ed
LDA buffer,X
BCS Le442
ADC #$3F
CMP #$1A
BCC Le4b1
Le442: ADC #$4F
CMP #$0A
BCC Le4b1
Le448: LDX synstkdx
Le44a: INY
LDA (synpag),Y
AND #$80
CMP #$20
BEQ Le4cd
LDA txtndxstk,X
STA text_index
LDA tokndxstk,X
STA token_index
```
I have not had a chance to try to dig into what was causing this, but using CA65 (which is what Jeff Tranter was using) fixed the issue and everything started working.
I would still like to figure out what is happening here, but just haven't had any spare cycles to spend on it.
## Credits and Recognition
First and most obvious, thanks to Steve 'Woz' Wozniak for creating Apple 1 Integer BASIC in the first place.