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Add functions to pop/push emulated CPU stack.

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This commit is contained in:
Radosław Kujawa 2017-01-20 22:03:03 +01:00
parent a50da41388
commit 7862703c88
2 changed files with 24 additions and 1 deletions
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20
src/instruction.c
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@ -220,3 +220,23 @@ instruction_data_read_1(rk65c02emu_t *e, instrdef_t *id, instruction_t *i)
return rv; return rv;
} }
/* put value onto the stack */
void
stack_push(rk65c02emu_t *e, uint8_t val)
{
bus_write_1(e->bus, STACK_START+e->regs.SP, val);
e->regs.SP--;
}
/* pull/pop value from the stack */
uint8_t
stack_pop(rk65c02emu_t *e)
{
uint8_t val;
val = bus_read_1(e->bus, STACK_START+e->regs.SP);
e->regs.SP++;
return val;
}

5
src/rk65c02.h
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@ -28,7 +28,10 @@ struct reg_state {
#define P_SIGN_OVERFLOW 0x40 #define P_SIGN_OVERFLOW 0x40
#define P_NEGATIVE 0x80 #define P_NEGATIVE 0x80
#define NEGATIVE P_NEGATIVE #define NEGATIVE P_NEGATIVE /* sign bit */
#define STACK_START 0x0100
#define STACK_END 0x01FF
typedef struct reg_state reg_state_t; typedef struct reg_state reg_state_t;