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/*
* psw.c
*
* Copyright (C) 2013 Hugo Villeneuve <hugo@hugovil.com>
*
* This file is released under the GPLv2
*/
#include "common.h"
#include "reg8051.h"
#include "memory.h"
/* Returns 0 or 1 */
int
psw_read_bit(int bit)
{
return (mem_read8(INT_MEM_ID, _PSW_) >> bit) & 0x01;
}
void
psw_write_bit(int bit, int val)
{
uint8_t psw = mem_read8(INT_MEM_ID, _PSW_);
if (val)
psw |= (1 << bit); /* Set */
else
psw &= ~(1 << bit); /* Clear */
mem_write8(INT_MEM_ID, _PSW_, psw); /* Save updated value */
}
/* Returns 0 or 1 */
int
psw_read_cy(void)
{
return psw_read_bit(PSW_BIT_CY);
}
void
psw_write_cy(int cy)
{
psw_write_bit(PSW_BIT_CY, cy);
}
void
psw_set_cy(void)
{
psw_write_bit(PSW_BIT_CY, 1);
}
void
psw_clr_cy(void)
{
psw_write_bit(PSW_BIT_CY, 0);
}
/* Returns 0 or 1 */
int
psw_read_ac(void)
{
return psw_read_bit(PSW_BIT_AC);
}
void
psw_write_ac(int ac)
{
psw_write_bit(PSW_BIT_AC, ac);
}
void
psw_set_ac(void)
{
psw_write_bit(PSW_BIT_AC, 1);
}
void
psw_clr_ac(void)
{
psw_write_bit(PSW_BIT_AC, 0);
}
/* Returns 0 or 1 */
int
psw_read_ov(void)
{
return psw_read_bit(PSW_BIT_OV);
}
void
psw_write_ov(int ov)
{
psw_write_bit(PSW_BIT_OV, ov);
}
void
psw_set_ov(void)
{
psw_write_bit(PSW_BIT_OV, 1);
}
void
psw_clr_ov(void)
{
psw_write_bit(PSW_BIT_OV, 0);
}
/*
* Compute parity of bits in accumulator:
* parity = 0: even number of ones in accumulator
* parity = 1: odd number of ones in accumulator
*/
void
psw_compute_parity_bit(void)
{
int parity = 0;
uint8_t acc = mem_read8(INT_MEM_ID, _ACC_);
while (acc) {
parity = !parity;
acc = acc & (acc - 1);
}
psw_write_bit(PSW_BIT_P, parity);
}
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