mirror of
https://github.com/cc65/cc65.git
synced 2024-12-24 11:31:31 +00:00
419eb700b5
The way we want to use the INITBSS segment - and especially the fact that it won't have the type bss on all ROM based targets - means that the name INITBSS is misleading. After all INIT is the best name from my perspective as it serves several purposes and therefore needs a rather generic name. Unfortunately this means that the current INIT segment needs to be renamed too. Looking for a short (ideally 4 letter) name I came up with ONCE as it contains all code (and data) accessed only once during initialization.
58 lines
1.8 KiB
ArmAsm
58 lines
1.8 KiB
ArmAsm
;
|
|
; IRQ handling (C128 version)
|
|
;
|
|
|
|
.export initirq, doneirq
|
|
.import callirq
|
|
|
|
.include "c128.inc"
|
|
|
|
; ------------------------------------------------------------------------
|
|
|
|
.segment "ONCE"
|
|
|
|
initirq:
|
|
lda IRQVec
|
|
ldx IRQVec+1
|
|
sta IRQInd+1
|
|
stx IRQInd+2
|
|
lda #<IRQStub
|
|
ldx #>IRQStub
|
|
jmp setvec
|
|
|
|
; ------------------------------------------------------------------------
|
|
|
|
.code
|
|
|
|
doneirq:
|
|
lda IRQInd+1
|
|
ldx IRQInd+2
|
|
setvec: sei
|
|
sta IRQVec
|
|
stx IRQVec+1
|
|
cli
|
|
rts
|
|
|
|
; ------------------------------------------------------------------------
|
|
; The C128 has ROM parallel to the RAM starting from $4000. The startup code
|
|
; above will change this setting so that we have RAM from $0000-$BFFF. This
|
|
; works quite well with the exception of interrupts: The interrupt handler
|
|
; is in ROM, and the ROM switches back to the ROM configuration, which means
|
|
; that parts of our program may not be accessible. To solve this, we place
|
|
; the following code into a special segment called "LOWCODE" which will be
|
|
; placed just above the startup code, so it goes into a RAM area that is
|
|
; not banked.
|
|
|
|
.segment "LOWCODE"
|
|
|
|
IRQStub:
|
|
cld ; Just to be sure
|
|
lda MMU_CR ; Get old register value
|
|
pha ; And save on stack
|
|
lda #MMU_CFG_CC65 ; Bank 0 with kernal ROM
|
|
sta MMU_CR
|
|
jsr callirq ; Call the functions
|
|
pla ; Get old register value
|
|
sta MMU_CR
|
|
jmp IRQInd ; Jump to the saved IRQ vector
|