add lsr, rol, ror

1 files changed, 24 insertions, 3 deletions

diff --git a/cpu.c b/cpu.c
index d754c15..5bd114e 100644
--- 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