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Flavioweb
Registered: Nov 2011
Posts: 463 |
[C128] Irq question ...
How can i make this code run on a C128 exactily at same addressess?
(I hope this isn't too much off-topic here...)
.C:3000 78 SEI
.C:3001 A9 7F LDA #$7F
.C:3003 8D 0D DC STA $DC0D
.C:3006 A9 00 LDA #$00
.C:3008 8D 14 03 STA $0314
.C:300b A9 40 LDA #$40
.C:300d 8D 15 03 STA $0315
.C:3010 A9 FF LDA #$FF
.C:3012 8D 12 D0 STA $D012
.C:3015 A9 01 LDA #$01
.C:3017 8D 1A D0 STA $D01A
.C:301a 4E 19 D0 LSR $D019
.C:301d 58 CLI
.C:301e 4C 1E 30 JMP $301E
.C:4000 EE 20 D0 INC $D020
.C:4003 EE 21 D0 INC $D021
.C:4006 AD 12 D0 LDA $D012
.C:4009 CD 12 D0 CMP $D012
.C:400c F0 FB BEQ $4009
.C:400e CE 20 D0 DEC $D020
.C:4011 CE 21 D0 DEC $D021
.C:4014 4E 19 D0 LSR $D019
.C:4017 4C 33 FF JMP $FF33 |
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Krill
Registered: Apr 2002
Posts: 2980 |
Not sure what your problem is, but the BASIC ROM on C-128 is at $4000, so you want to disable it in order to use the interrupt handler:lda #$02
sta $ff00 What's the background of your question? |
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Flavioweb
Registered: Nov 2011
Posts: 463 |
The problem is here:
ff17 48 PHA - A:00 X:17 Y:00 SP:17 - I
ff18 8A TXA - A:00 X:17 Y:00 SP:16 - I
ff19 48 PHA - A:17 X:17 Y:00 SP:16 - I
ff1a 98 TYA - A:17 X:17 Y:00 SP:15 - I
ff1b 48 PHA - A:00 X:17 Y:00 SP:15 - IZ
ff1c AD 00 FF LDA $FF00 - A:00 X:17 Y:00 SP:14 - IZ
ff1f 48 PHA - A:00 X:17 Y:00 SP:14 - IZ
ff20 A9 00 LDA #$00 - A:00 X:17 Y:00 SP:13 - IZ
ff22 8D 00 FF STA $FF00 - A:00 X:17 Y:00 SP:13 - IZ
ff25 BA TSX - A:00 X:17 Y:00 SP:13 - IZ
ff26 BD 05 01 LDA $0105,X - A:00 X:13 Y:00 SP:13 - I
ff29 29 10 AND #$10 - A:20 X:13 Y:00 SP:13 - I
ff2b F0 03 BEQ $FF30 - A:00 X:13 Y:00 SP:13 - IZ
ff30 6C 14 03 JMP ($0314) - A:00 X:13 Y:00 SP:13 - IZ
at $FF20 kernal set $FF00 to $00 turning on BASIC again...
There is a way to avoid this but having kernal (not BASIC) rom active? |
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Krill
Registered: Apr 2002
Posts: 2980 |
Ah, i see. Then you either want to disable the KERNAL ROM as well and have your entirely own interrupt handler with the vector at $fffe, or you let the vector at $0314 point to a thunk residing anywhere below $4000, which would disable the BASIC ROM and then jump to the actual handler at $4000. |
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Flavioweb
Registered: Nov 2011
Posts: 463 |
I need to have kernal on but basic off, using vector at $0314 to point the IRQ routine at $4000... |
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Krill
Registered: Apr 2002
Posts: 2980 |
Okay, XY problem solving time. What is your _actual_ problem you're trying to solve? |
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Flavioweb
Registered: Nov 2011
Posts: 463 |
I'm experimenting using CC65 with a mix of C and assembly code.
An IRQ handler that setup one raster irq is called by C code.
Compiled C code starts with:
.C:1c0d A9 0E LDA #$0E
.C:1c0f 20 D2 FF JSR $FFD2
.C:1c12 AD 00 FF LDA $FF00
.C:1c15 48 PHA
.C:1c16 A9 0E LDA #$0E
.C:1c18 8D 00 FF STA $FF00
so ROMS are OFF.
Irq setup code starts at $4xxx and looks like:
.C:4011 A9 7F LDA #$7F
.C:4013 8D 0D DC STA $DC0D
.C:4016 78 SEI
.C:4017 A9 44 LDA #$44
.C:4019 8D 14 03 STA $0314
.C:401c A9 40 LDA #$40
.C:401e 8D 15 03 STA $0315
.C:4021 A9 64 LDA #$64
.C:4023 8D 18 03 STA $0318
.C:4026 A9 40 LDA #$40
.C:4028 8D 19 03 STA $0319
.C:402b A9 01 LDA #$01
.C:402d 8D 1A D0 STA $D01A
.C:4030 A9 1B LDA #$1B
.C:4032 8D 11 D0 STA $D011
.C:4035 A9 FC LDA #$FC
.C:4037 8D 12 D0 STA $D012
.C:403a AD 0D DC LDA $DC0D
.C:403d A9 0E LDA #$0E
.C:403f 8D 00 FF STA $FF00
.C:4042 58 CLI
.C:4043 60 RTS
which have a (now i know) useless $FF00 write at $403d.
After CLI at $4042, first time IRQ is triggered i have BASIC rom turned ON by kernal IRQ code... and all fucks up.
There is a way to keep BASIC OFF? |
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Krill
Registered: Apr 2002
Posts: 2980 |
But why must your interrupt handler start at $4000 and not, say, $3f80? And is that interrupt handler thunk/trampoline i mentioned not an option? |
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Flavioweb
Registered: Nov 2011
Posts: 463 |
Because it look a really stupid thing to me...
I take it as last chance. Is a useless waste of cycles.
If i want to use ram under basic i need to set a code in the ram accessible by defalut, then set $FF00 and jmp to irq code.
I'm trying to understand if there is a way to "reconfigure" the bank activated by $00 in $FF00 to keep only kernal ON...
But is just my guess... i don't know if there is a way to do it... |
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Krill
Registered: Apr 2002
Posts: 2980 |
There isn't.
If the number of cycles is a problem for you, why not disable the ROM altogether and have your own interrupt handler called directly via $fffe/f? Would both consume a minimal amount of cycles and not have the BASIC ROM problem. |
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Krill
Registered: Apr 2002
Posts: 2980 |
Besides, having interrupt handlers below $4000 (or at $c000+) is a good idea because of the two RAM banks. You really want to enable a common area (configurable to up to 16K) and put your interrupt handlers there, otherwise having interrupt handlers in one bank and the code being interrupted in another could be a bit of a nuisance. |
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