; Startup code for cc65 (C128 version)
;
- .export _exit
+ .export _exit
.export __STARTUP__ : absolute = 1 ; Mark as startup
- .import callirq, initlib, donelib
- .import zerobss
- .import push0, callmain
+ .import initlib, donelib
+ .import zerobss
+ .import push0, callmain
.import RESTOR, BSOUT, CLRCH
- .import __INTERRUPTOR_COUNT__
- .import __RAM_START__, __RAM_SIZE__
+ .import __MAIN_START__, __MAIN_SIZE__, __STACKSIZE__
+ .importzp ST
.include "zeropage.inc"
- .include "c128.inc"
+ .include "c128.inc"
-; ------------------------------------------------------------------------
-; Constants
-
-IRQInd = $2FD ; JMP $0000 - used as indirect IRQ vector
-
-; ------------------------------------------------------------------------
-; BASIC header with a SYS call
-
-.segment "EXEHDR"
-
- .word Head ; Load address
-Head: .word @Next
- .word .version ; Line number
- .byte $9E ; SYS token
- .byte <(((Start / 1000) .mod 10) + '0')
- .byte <(((Start / 100) .mod 10) + '0')
- .byte <(((Start / 10) .mod 10) + '0')
- .byte <(((Start / 1) .mod 10) + '0')
- .byte $00 ; End of BASIC line
-@Next: .word 0 ; BASIC end marker
-
; ------------------------------------------------------------------------
; Startup code
-.segment "STARTUP"
+.segment "STARTUP"
Start:
-; Switch to the second charset
-
- lda #14
- jsr BSOUT
-
-; Before doing anything else, we have to setup our banking configuration.
-; Otherwise just the lowest 16K are actually RAM. Writing through the ROM
-; to the underlying RAM works, but it is bad style.
+; Switch to the second charset.
- lda MMU_CR ; Get current memory configuration...
- pha ; ...and save it for later
- lda #MMU_CFG_CC65 ; Bank0 with kernal ROM
- sta MMU_CR
+ lda #14
+ jsr BSOUT
-; Save the zero page locations we need
+; Before doing anything else, we have to set up our banking configuration.
+; Otherwise, just the lowest 16K are actually RAM. Writing through the ROM
+; to the underlying RAM works; but, it is bad style.
- ldx #zpspace-1
-L1: lda sp,x
- sta zpsave,x
- dex
- bpl L1
+ lda MMU_CR ; Get current memory configuration...
+ pha ; ...and save it for later
+ lda #MMU_CFG_CC65 ; Bank0 with Kernal ROM
+ sta MMU_CR
-; Clear the BSS data
+; Save the zero-page locations that we need.
- jsr zerobss
+ ldx #zpspace-1
+L1: lda sp,x
+ sta zpsave,x
+ dex
+ bpl L1
-; Save system stuff and setup the stack
+; Clear the BSS data.
- pla ; Get MMU setting
- sta mmusave
+ jsr zerobss
- tsx
- stx spsave ; Save the system stack pointer
+; Save some system stuff; and, set up the stack.
- lda #<(__RAM_START__ + __RAM_SIZE__)
- sta sp
- lda #>(__RAM_START__ + __RAM_SIZE__)
- sta sp+1 ; Set argument stack ptr
+ pla ; Get MMU setting
+ sta mmusave
-; If we have IRQ functions, chain our stub into the IRQ vector
+ tsx
+ stx spsave ; Save the system stack pointer
- lda #<__INTERRUPTOR_COUNT__
- beq NoIRQ1
- lda IRQVec
- ldx IRQVec+1
- sta IRQInd+1
- stx IRQInd+2
- lda #<IRQStub
- ldx #>IRQStub
- sei
- sta IRQVec
- stx IRQVec+1
- cli
+ lda #<(__MAIN_START__ + __MAIN_SIZE__ + __STACKSIZE__)
+ ldx #>(__MAIN_START__ + __MAIN_SIZE__ + __STACKSIZE__)
+ sta sp
+ stx sp+1 ; Set argument stack ptr
-; Call module constructors
+; Call the module constructors.
-NoIRQ1: jsr initlib
+ jsr initlib
-; Set the bank for the file name to our execution bank. We must do this,
-; *after* calling constructors, because some of them may depend on the
-; original value of this register.
+; Set the bank for the file name to our execution bank. We must do this
+; *after* calling the constructors because some of them might depend on
+; the original value of this register.
lda #0
sta FNAM_BANK
-; Push arguments and call main()
+; Push the command-line arguments; and, call main().
jsr callmain
-; Back from main (this is also the _exit entry). Run module destructors
+; Back from main() [this is also the exit() entry]. Run the module destructors.
-_exit: jsr donelib
+_exit: pha ; Save the return code on stack
+ jsr donelib
-; Reset the IRQ vector if we chained it.
+; Copy back the zero-page stuff.
- pha ; Save the return code on stack
- lda #<__INTERRUPTOR_COUNT__
- beq NoIRQ2
- lda IRQInd+1
- ldx IRQInd+2
- sei
- sta IRQVec
- stx IRQVec+1
- cli
+ ldx #zpspace-1
+L2: lda zpsave,x
+ sta sp,x
+ dex
+ bpl L2
-; Copy back the zero page stuff
+; Place the program return code into BASIC's status variable.
-NoIRQ2: ldx #zpspace-1
-L2: lda zpsave,x
- sta sp,x
- dex
- bpl L2
+ pla
+ sta ST
-; Place the program return code into ST
+; Reset the stack and the memory configuration.
- pla
- sta ST
+ ldx spsave
+ txs
+ ldx mmusave
+ stx MMU_CR
-; Reset the stack and the memory configuration
-
- ldx spsave
- txs
- ldx mmusave
- stx MMU_CR
-
-; Done, restore kernal vectors in an attempt to cleanup
-
- jmp RESTOR
-
-; ------------------------------------------------------------------------
-; 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
+; Done, return to BASIC.
+ rts
; ------------------------------------------------------------------------
; Data
-.segment "ZPSAVE"
+.segment "INIT"
-zpsave: .res zpspace
-
-.bss
-spsave: .res 1
-mmusave:.res 1
+zpsave: .res zpspace
+; ------------------------------------------------------------------------
+.bss
+spsave: .res 1
+mmusave:.res 1
projects / cc65 / blobdiff