From a3189d90af2c675086e6dd629cfa071e4d75d4c9 Mon Sep 17 00:00:00 2001
From: vin <git@vineetk.net>
Date: Mon, 10 Jun 2024 23:25:49 +0530
Subject: [PATCH] add jsr, rti, rts

---
 cpu.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/cpu.c b/cpu.c
index e63760c..87d68c8 100644
--- a/cpu.c
+++ b/cpu.c
@@ -407,15 +407,23 @@ iny(uint8_t arg)
 }
 
 static void
-jmp(uint8_t arg)
+jmp(uint16_t arg)
 {
 	regs.pc = arg;
 }
 
 static void
-jsr(uint8_t arg)
+jsr(uint16_t arg)
 {
-/* TODO: complete this */
+	uint16_t tmp = regs.pc + 2;
+
+	/*
+	 * first push high-byte of return address then low-byte
+	 * https://www.masswerk.at/6502/6502_instruction_set.html
+	 */
+	PUSH((tmp & 0xFF00) >> 8);
+	PUSH(tmp & 0xFF);
+	regs.pc = arg;
 }
 
 static void
@@ -547,13 +555,14 @@ ror(uint8_t arg)
 static void
 rti(uint8_t arg)
 {
-/* TODO: complete this */
+	plp();
+	regs.pc = PULL();
 }
 
 static void
-rts(uint8_t arg)
+rts(void)
 {
-/* TODO: complete this */
+	regs.pc = PULL() + 1;
 }
 
 static void
@@ -1186,7 +1195,7 @@ interpret(void)
 			cycles += 6;
 			break;
 		case 0x60:
-			rts(opcode_arg(AM_ACC));
+			rts();
 			cycles += 6;
 			break;
 		case 0xe9: