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Add some comments about the IRQ oddities.

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Jeremy Rand 2016-12-16 00:05:26 -05:00
parent cbb37cae43
commit 21325bbb0f
1 changed files with 9 additions and 0 deletions
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mocktest/mockingboard_speech.s
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@ -35,6 +35,15 @@ _outptr: .byte $00, $00
_endptr: .byte $00, $00
_mockingBoardSpeechBusy: .byte $00
_mockingBoardSpeechPlaying: .byte $00
; This is a JMP instruction followed by the address of the old interrupt vector.
; It serves two purposes:
; - The interrupt handler in this file can jump to this location to jump to the
; old interrupt vector
; - This code can restore the old vector when the speech code is shutdown
; Better would be to intergrate into the cc65 IRQ functionality but I found I couldn't
; make that work for some unknown reason. Instead, this interrupt service routine
; chains the cc65 one.
_irqLandingPad: .byte $4C, $00, $00