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Add an example of 8-bit multiplication.

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This commit is contained in:
Radosław Kujawa 2019-01-10 10:27:44 +01:00
parent e3714fe805
commit 327d60932e
3 changed files with 86 additions and 1 deletions
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5
examples/Makefile
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@ -15,7 +15,7 @@ RK6502LIB=../src/librk65c02.a
VASM=vasm6502_std
VASMFLAGS=-Fbin -wdc02
EXAMPLES=min3
EXAMPLES=min3 mul_8bit_to_8bits
EXAMPLES_ROMS:=$(addsuffix .rom,$(basename $(wildcard *.s)))
all : $(EXAMPLES) $(EXAMPLES_ROMS)
@ -23,6 +23,9 @@ all : $(EXAMPLES) $(EXAMPLES_ROMS)
min3 : min3.o $(RK6502LIB)
$(CC) -o $@ $(LDFLAGS) $< $(RK6502LIB)
mul_8bit_to_8bits : mul_8bit_to_8bits.o $(RK6502LIB)
$(CC) -o $@ $(LDFLAGS) $< $(RK6502LIB)
%.rom : %.s
$(VASM) $(VASMFLAGS) -o $@ $<

32
examples/mul_8bit_to_8bits.c Normal file
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@ -0,0 +1,32 @@
#include <stdio.h>
#include <stdint.h>
#include "rk65c02.h"
#include "bus.h"
#include "log.h"
#include "instruction.h"
static const uint16_t load_addr = 0xC000;
int main(void)
{
uint8_t num1, num2;
uint8_t res;
rk65c02emu_t e;
e = rk65c02_load_rom("mul_8bit_to_8bits.rom", load_addr, NULL);
e.regs.SP = 0xFF;
e.regs.PC = load_addr;
num1 = 4; num2 = 8;
stack_push(&e, num1);
stack_push(&e, num2);
rk65c02_start(&e);
res = stack_pop(&e);
printf("Result of multiplication: %d\n", res);
}

50
examples/mul_8bit_to_8bits.s Normal file
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@ -0,0 +1,50 @@
.org 0xC000
start: jsr mul_8bit_to_8bits
stp
; mul_8bit_to_8bits
; Multiplies 2 numbers (passed on stack) and returns result on stack.
; General 8bit * 8bit = 8bit multiply
; by White Flame 20030207
; adapted as rk65c02 example by rkujawa
; Instead of using a bit counter, this routine early-exits when num2 reaches
; zero, thus saving iterations.
; .X and .Y are preserved
; num1 and num2 get clobbered
.set num1,0x10
.set num2,0x11
.set retl,0x12
.set reth,0x13
mul_8bit_to_8bits:
pla ; pull return address
sta retl
pla
sta reth
pla ; pull num1 from stack
sta num1
pla ; pull num2 from stack
sta num2
lda #0x00
beq enterl
doAdd: clc
adc num1
loop: asl num1
; For an accumulating multiply (A = A + num1 * num2),
; set up num1 and num2, then enter here.
enterl: lsr num2
bcs doAdd
bne loop
end:
pha ; save result to stack
lda reth ; restore return address
pha
lda retl
pha
rts ; return from function