emu_nes

commit 5535e5de70684dd8406e53d6ce928faf9011336c
parent 4b7fae00103c9fbaeeba45a78a7d0c910d243dc0
Author: vin <git@vineetk.net>
Date:   Sun, 30 Jun 2024 06:28:41 -0400

change SBC to be ADC with one's complement instead of two's

It seems that is what was expected when run with nestest.

Diffstat:
M
cpu.c
 | 
8
+++++---

1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/cpu.c b/cpu.c
@@ -664,7 +664,7 @@ static void
 sbc(uint8_t arg)
 {
 	/* SBC is described online as ADC with argument as two's complement */
-	adc(~arg + 1);
+	adc(~arg);
 }
 
 static void
@@ -733,7 +733,8 @@ tay(void)
 static void
 tsx(void)
 {
-	regs.x = PULL();
+//	regs.x = PULL();
+	regs.x = regs.sp;
 
 	STATUS_UPDATE_ZERO(regs.x);
 	STATUS_UPDATE_NEGATIVE(regs.x);
@@ -751,7 +752,8 @@ txa(void)
 static void
 txs(void)
 {
-	PUSH(regs.x);
+//	PUSH(regs.x);
+	regs.sp = regs.x;
 }
 
 static void