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NEC ADD4S instruction (#10)

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Cacodemon345
2022-09-06 02:27:09 +06:00
committed by GitHub
parent 323f7e7a62
commit e93cd46c78
1 changed files with 36 additions and 0 deletions
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36
src/cpu/808x.c
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@@ -1824,6 +1824,42 @@ execx86(int cycs)
handled = 1;
break;
}
case 0x20: /* ADD4S */
{
uint8_t odd = !!(CL % 2);
uint8_t zero = 1;
uint8_t nibbles_count = CL - odd;
uint32_t i = 0, carry = 0, nibble = 0;
uint32_t srcseg = ovr_seg ? *ovr_seg : DS;
srcseg <<= 4;
wait(5, 0);
for (i = 0; i < ((nibbles_count / 2) + odd); i++) {
wait(19, 0);
for (nibble = 0; nibble < 2; nibble++) {
uint8_t destbyte = read_mem_b((ES << 4) + DI + i) >> (nibble ? 4 : 0);
uint8_t srcbyte = read_mem_b(srcseg + SI + i) >> (nibble ? 4 : 0);
destbyte &= 0xF;
srcbyte &= 0xF;
uint8_t nibble_result = destbyte + srcbyte + carry;
carry = 0;
while (nibble_result >= 10) {
nibble_result -= 10;
carry++;
}
if (zero != 0) zero = (nibble_result == 0);
write_mem_b((ES << 4) + DI + i, (read_mem_b((ES << 4) + DI + i) & (nibble ? 0x0F : 0xF0)) | (nibble_result << (4 * nibble)));
if (i == ((nibbles_count / 2)) && odd && nibble == 0) {
zero = ((read_mem_b((ES << 4) + DI + i) & 0xF0) == 0);
break;
}
}
}
set_cf(!!carry);
set_zf(!!zero);
handled = 1;
break;
}
case 0x31: /* INS reg1, reg2 */
case 0x39: /* INS reg8, imm4 */
{