Apple-2-SW/apple2a
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Brad Grantham 2018-07-27 22:30:44 -07:00
commit d30e8778d5
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26
Makefile Normal file
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CC65 = $(HOME)/trees/cc65/bin/
CPU = 6502
a.out: main.o interrupt.o vectors.o apple2rom.cfg apple2rom.lib
$(CC65)/ld65 -C apple2rom.cfg -m main.map --dbgfile main.dbg interrupt.o vectors.o main.o apple2rom.lib
clean:
rm *.o a.out main.s
main.s: main.c
$(CC65)/cc65 -t none -O --cpu $(CPU) main.c
main.o: main.s
$(CC65)/ca65 --cpu $(CPU) main.s
interrupt.o: interrupt.s
$(CC65)/ca65 --cpu $(CPU) interrupt.s
vectors.o: vectors.s
$(CC65)/ca65 --cpu $(CPU) vectors.s
crt0.o: crt0.s
$(CC65)/ca65 --cpu $(CPU) crt0.s
apple2rom.lib: crt0.o
../cc65/bin/ar65 a apple2rom.lib crt0.o

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apple2rom.cfg Normal file
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MEMORY {
ZP: start = $0, size = $100, type = rw, define = yes;
RAM: start = $4000, size = $4000, define = yes;
ROM: start = $D000, size = $3000, file = %O;
}
SEGMENTS {
ZEROPAGE: load = ZP, type = zp, define = yes;
DATA: load = ROM, type = rw, define = yes, run = RAM;
BSS: load = RAM, type = bss, define = yes;
HEAP: load = RAM, type = bss, optional = yes;
STARTUP: load = ROM, type = ro;
ONCE: load = ROM, type = ro, optional = yes;
CODE: load = ROM, type = ro;
RODATA: load = ROM, type = ro;
VECTORS: load = ROM, type = ro, start = $FFFA;
}
FEATURES {
CONDES: segment = STARTUP,
type = constructor,
label = __CONSTRUCTOR_TABLE__,
count = __CONSTRUCTOR_COUNT__;
CONDES: segment = STARTUP,
type = destructor,
label = __DESTRUCTOR_TABLE__,
count = __DESTRUCTOR_COUNT__;
}
SYMBOLS {
# Define the stack size for the application
__STACKSIZE__: value = $0200, type = weak;
# __STACKSIZE__: type = weak, value = $0800; # 2k stack
}

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apple2rom.lib Normal file
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crt0.s Normal file
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; ---------------------------------------------------------------------------
; crt0.s
; ---------------------------------------------------------------------------
;
; Startup code for cc65 (Single Board Computer version)
.export _init, _exit
.import _main
.export __STARTUP__ : absolute = 1 ; Mark as startup
.import __RAM_START__, __RAM_SIZE__ ; Linker generated
.import copydata, zerobss, initlib, donelib
.include "zeropage.inc"
; ---------------------------------------------------------------------------
; Place the startup code in a special segment
.segment "STARTUP"
; ---------------------------------------------------------------------------
; A little light 6502 housekeeping
_init: LDX #$FF ; Initialize stack pointer to $01FF
TXS
CLD ; Clear decimal mode
; ---------------------------------------------------------------------------
; Set cc65 argument stack pointer
LDA #<(__RAM_START__ + __RAM_SIZE__)
STA sp
LDA #>(__RAM_START__ + __RAM_SIZE__)
STA sp+1
; ---------------------------------------------------------------------------
; Initialize memory storage
JSR zerobss ; Clear BSS segment
JSR copydata ; Initialize DATA segment
JSR initlib ; Run constructors
; ---------------------------------------------------------------------------
; Call main()
JSR _main
; ---------------------------------------------------------------------------
; Back from main (this is also the _exit entry): force a software break
_exit: JSR donelib ; Run destructors
BRK

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interrupt.s Normal file
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; ---------------------------------------------------------------------------
; interrupt.s
; ---------------------------------------------------------------------------
;
; Interrupt handler.
;
; Checks for a BRK instruction and returns from all valid interrupts.
.import _stop
.export _irq_int, _nmi_int
.segment "CODE"
.PC02 ; Force 65C02 assembly mode
; ---------------------------------------------------------------------------
; Non-maskable interrupt (NMI) service routine
_nmi_int: RTI ; Return from all NMI interrupts
; ---------------------------------------------------------------------------
; Maskable interrupt (IRQ) service routine
_irq_int: PHX ; Save X register contents to stack
TSX ; Transfer stack pointer to X
PHA ; Save accumulator contents to stack
INX ; Increment X so it points to the status
INX ; register value saved on the stack
LDA $100,X ; Load status register contents
AND #$10 ; Isolate B status bit
BNE break ; If B = 1, BRK detected
; ---------------------------------------------------------------------------
; IRQ detected, return
irq: PLA ; Restore accumulator contents
PLX ; Restore X register contents
RTI ; Return from all IRQ interrupts
; ---------------------------------------------------------------------------
; BRK detected, stop
break: JMP break ; If BRK is detected, something very bad
; has happened, so stop running

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main.c Normal file
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char *title = "Apple IIa";
unsigned char title_length = 9;
unsigned char *text_page1_base = (unsigned char *)0x400;
int main(void)
{
int offset = (80 - title_length) / 2;
unsigned char *loc = text_page1_base + offset;
int i;
for(i = 0; i < 80 * 24; i++)
text_page1_base[i] = ' ' | 0x80;
for(i = 0; i < title_length; i++)
loc[i] = title[i] | 0x80;
while(1);
}

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vectors.s Normal file
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; ---------------------------------------------------------------------------
; vectors.s
; ---------------------------------------------------------------------------
;
; Defines the interrupt vector table.
.import _init
.import _nmi_int, _irq_int
.segment "VECTORS"
.addr _nmi_int ; NMI vector
.addr _init ; Reset vector
.addr _irq_int ; IRQ/BRK vector