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Merge branch 'master' into c_sp

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Gorilla Sapiens
2025-06-18 06:14:39 +00:00
parent 2f55eeb612 02d22e712c
commit 5a4b11e7ff
43 changed files with 1815 additions and 197 deletions
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68
libsrc/plus4/crt0.s
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@@ -9,8 +9,7 @@
.import callirq_y, initlib, donelib
.import callmain, zerobss
.import __INTERRUPTOR_COUNT__
.import __MAIN_START__, __MAIN_SIZE__ ; Linker generated
.import __STACKSIZE__ ; Linker generated
.import __HIMEM__ ; Linker generated
.importzp ST
.include "zeropage.inc"
@@ -52,19 +51,28 @@ L1: lda c_sp,x
tsx
stx spsave ; Save system stk ptr
lda #<(__MAIN_START__ + __MAIN_SIZE__ + __STACKSIZE__)
ldx #>(__MAIN_START__ + __MAIN_SIZE__ + __STACKSIZE__)
lda #<__HIMEM__
ldx #>__HIMEM__
sta c_sp
stx c_sp+1
; Set up the IRQ vector in the banked RAM; and, switch off the ROM.
ldx #<IRQ
ldy #>IRQ
lda #<IRQ
ldx #>IRQ
sei ; No ints, handler not yet in place
sta ENABLE_RAM
stx $FFFE ; Install interrupt handler
sty $FFFF
sta $FFFE ; Install interrupt handler
stx $FFFF
lda IRQVec
ldx IRQVec+1
sta IRQInd+1
stx IRQInd+2
lda #<IRQStub
ldx #>IRQStub
sta IRQVec
stx IRQVec+1
cli ; Allow interrupts
; Clear the BSS data.
@@ -95,6 +103,13 @@ _exit: pha ; Save the return code
lda #0
sta irqcount ; Disable custom IRQ handlers
sei
ldx IRQInd+1
ldy IRQInd+2
stx IRQVec
sty IRQVec+1
cli
; Copy back the zero-page stuff.
ldx #zpspace-1
@@ -122,9 +137,13 @@ L2: lda zpsave,x
; IRQ handler. The handler in the ROM enables the Kernal, and jumps to
; $CE00, where the ROM code checks for a BRK or IRQ, and branches via the
; indirect vectors at $314/$316.
; To make our stub as fast as possible, we skip the whole part of the ROM
; handler, and jump to the indirect vectors directly. We do also call our
; own interrupt handlers if we have any; so, they need not use $314.
;
; When RAM is banked in, we skip the whole part of the ROM handler, and jump to
; the indirect vectors directly, after calling our own interrupt handlers.
;
; When ROM is banked in, a stub installed in the $314 indirect vector ensures
; that our interrupt handlers are still called (otherwise, interrupts that are
; not serviced by the ROM handler may cause a deadlock).
.segment "LOWCODE"
@@ -139,15 +158,6 @@ IRQ: cld ; Just to be sure
and #$10 ; Test for BRK bit
bne dobreak
; It's an IRQ; and, RAM is enabled. If we have handlers, call them. We will use
; a flag here instead of loading __INTERRUPTOR_COUNT__ directly, since the
; condes function is not reentrant. The irqcount flag will be set/reset from
; the main code, to avoid races.
ldy irqcount
beq @L1
jsr callirq_y ; Call the IRQ functions
; Since the ROM handler will end with an RTI, we have to fake an IRQ return
; on the stack, so that we get control of the CPU after the ROM handler,
; and can switch back to RAM.
@@ -161,7 +171,7 @@ IRQ: cld ; Just to be sure
pha ; Push faked X register
pha ; Push faked Y register
sta ENABLE_ROM ; Switch to ROM
jmp (IRQVec) ; Jump indirect to Kernal IRQ handler
jmp (IRQVec) ; Jump indirect to IRQ stub
irq_ret:
sta ENABLE_RAM ; Switch back to RAM
@@ -183,6 +193,22 @@ nohandler:
sta ENABLE_ROM
jmp (BRKVec) ; Jump indirect to the break vector
; IRQ stub installed at $314, called by our handler above if RAM is banked in,
; or the Kernal IRQ handler if ROM is banked in.
; If we have handlers, call them. We will use a flag here instead of loading
; __INTERRUPTOR_COUNT__ directly, since the condes function is not reentrant.
; The irqcount flag will be set/reset from the main code, to avoid races.
IRQStub:
cld ; Just to be sure
sta ENABLE_RAM
ldy irqcount
beq @L1
jsr callirq_y ; Call the IRQ functions
@L1: sta ENABLE_ROM
jmp (IRQInd+1) ; Jump to the saved IRQ vector
; ------------------------------------------------------------------------
; Data