emu_nes

commit dbb952a52b1b7168b4d1e98e9819d632ad16e087
parent ebdf50cdf3a357a0e37a5751fd9d78ae975979a0
Author: vin <git@vineetk.net>
Date:   Mon, 10 Jun 2024 14:27:53 +0530

add lsr, rol, ror

Diffstat:
M
cpu.c
 | 
27
++++++++++++++++++++++++---

1 file changed, 24 insertions(+), 3 deletions(-)
diff --git a/cpu.c b/cpu.c
@@ -443,7 +443,12 @@ ldy(uint8_t arg)
 static void
 lsr(uint8_t arg)
 {
-/* TODO: complete this */
+	regs.status.carry = regs.a & 1;	// bit 0 in carry
+	regs.a >>= 1;
+	regs.a &= ~(1 << 7);		// bit 7 cleared
+
+	STATUS_UPDATE_ZERO(regs.a);
+	STATUS_UPDATE_NEGATIVE(regs.a);
 }
 
 static void
@@ -512,13 +517,29 @@ ply(uint8_t arg)
 static void
 rol(uint8_t arg)
 {
-/* TODO: complete this */
+	uint8_t tmp;
+	tmp = (regs.a & (1 << 7)) > 0;
+
+	regs.a <<= 1;
+	regs.a |= regs.status.carry;
+
+	regs.status.carry = tmp;
+	STATUS_UPDATE_ZERO(regs.a);
+	STATUS_UPDATE_NEGATIVE(regs.a);
 }
 
 static void
 ror(uint8_t arg)
 {
-/* TODO: complete this */
+	uint8_t tmp;
+	tmp = regs.a & 1;
+
+	regs.a >>= 1;
+	regs.a |= regs.status.carry << 7;
+
+	regs.status.carry = tmp;
+	STATUS_UPDATE_ZERO(regs.a);
+	STATUS_UPDATE_NEGATIVE(regs.a);
 }
 
 static void