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Correctly map out ROM when needed in the "phantom keys" workaround.

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This commit is contained in:
Christian Groessler
2014-04-26 11:55:24 +02:00
parent 54be6de9bc
commit 6307815ada
3 changed files with 55 additions and 33 deletions
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40
libsrc/c128/mou/c128-1351.s
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@@ -66,15 +66,6 @@ CMOVEY: jmp $0000 ; Move the cursor to Y coord
SCREEN_HEIGHT = 200
SCREEN_WIDTH = 320
;----------------------------------------------------------------------------
; data segment
.data
chainIRQ:
.byte $4c ; JMP opcode
.word 0 ; pointer to ROM IRQ handler (will be set at runtime)
;----------------------------------------------------------------------------
; Global variables. The bounding box values are sorted so that they can be
; written with the least effort in the SETBOX and GETBOX routines, so don't
@@ -103,6 +94,10 @@ Buttons: .res 1 ; Button mask
old_key_count: .res 1
; original IRQ vector
old_irq: .res 2
.rodata
; Default values for above variables
@@ -158,20 +153,27 @@ INSTALL:
; Initialize our IRQ magic
lda IRQInd+1
sta chainIRQ+1
; remember ROM IRQ continuation address
lda IRQInd+2
sta chainIRQ+2
sta old_irq+1
lda IRQInd+1
sta old_irq
lda libref
sta ptr3
lda libref+1
sta ptr3+1
; set ROM IRQ continuation address to point to the provided routine
ldy #2
lda (ptr3),y
sta IRQInd+1
iny
lda (ptr3),y
sta IRQInd+2
; set address of our IRQ callback routine
; since it's called via "rts" we have to use "address-1"
iny
lda #<(callback-1)
sta (ptr3),y
@@ -179,10 +181,16 @@ INSTALL:
lda #>(callback-1)
sta (ptr3),y
iny
lda #<(chainIRQ-1)
; set ROM entry point vector
; since it's called via "rts" we have to decrement it by one
lda old_irq
sec
sbc #1
sta (ptr3),y
iny
lda #>(chainIRQ-1)
lda old_irq+1
sbc #0
sta (ptr3),y
cli
@@ -197,10 +205,10 @@ INSTALL:
; No return code required (the driver is removed from memory on return).
UNINSTALL:
lda chainIRQ+1
lda old_irq
sei
sta IRQInd+1
lda chainIRQ+2
lda old_irq+1
sta IRQInd+2
cli