King Tut.csm what's going on?

matsondawson · Post by **matsondawson** » Mon Aug 31, 2009 3:39 am

I'm trying to load King Tut from tape, and it keeps failing with the following (below). The question is what's the JMP ($0014) meant to do.
And, given the program below, why is line 18 poking stuff to the keyboard buffer and what's the inverted "E".

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DCB8 STY $68
DCBA RTS

D804 LDA $64
D806 LDY $65
D808 STY $14
D80A STA $15
D80C RTS

E12D LDA #$E1
E12F PHA
E130 LDA #$43
E132 PHA
E133 LDA $030F
E136 PHA
E137 LDA $030C
E13A LDX $030D
E13D LDY $030E
E140 PLP
E141 JMP ($0014)
1101 ???err 239
bad instruction: EF pc:1102

Mike · Post by **Mike** » Mon Aug 31, 2009 3:55 am

matsondawson wrote:The question is what's the JMP ($0014) meant to do.

It's part of the routine in the BASIC interpreter, that handles the SYS command. JMP ($0014) calls the routine specified in the numeric parameter of SYS. The return address $E144 - 1 is pushed on the stack in the instructions of $E12D .. $E132.

And, given the program below, why is line 18 poking stuff to the keyboard buffer and what's the inverted "E".

Standard procedure to LOAD and RUN the next program from tape. It simulates SHIFT+[RUN STOP]. And the "inverted E" switches to white colour, so you don't see the "PRESS PLAY ON TAPE", etc... prompts.

This header program seems to be pretty useless, anyway. At least the following program will set 45/46 to new values, and the POKEs to 43/44 refer to an unexpanded VIC-20. What RAM configuration does the game demand?

matsondawson · Post by **matsondawson** » Mon Aug 31, 2009 4:15 am

I believe it's an unexpanded game.
If I skip that loader and just load normally it seems to work.
I think there's something wrong with my tape load routines, as if i type the program in by hand it works fine, but if i load it and run, it does that bad branch.

Thanks for the help.

Mayhem · Post by **Mayhem** » Mon Aug 31, 2009 9:09 am

The TAP in GB20 loads and runs fine, maybe it's the emulator? Cheers for that screen though, tells me who programmed it to enter into the database! Another John Ferrari program (sadly RIP), who went onto do Summer and Winter Camp for Thalamus for example.

matsondawson · Post by **matsondawson** » Wed Sep 02, 2009 5:53 am

ok King Tut code sucks...
I was trying to load the csm of it, that failed, then I tried the tap and that failed the same way.
I loaded up vice and added a break point, and it turns out there's some dodgy code in king tuts start routine.

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ISB $5554     <- undocumented instruction
NOOP $0F,X   <- same.  what the!?
LDA #$02
LDA #$64
STA $0328
RTS

I think it's branching 4 bytes too early in the code.
I haven't implemented undocumented instructions yet which explains why it doesn't work for me.

nbla000 · Post by **nbla000** » Wed Sep 02, 2009 8:00 am

I've downloaded a tap file here and seems that works.

Btw it works for unexpanded vics only, tested on last Vice version.