From bb3f77ec7fd184803f1fa3fdd687a77ba969c1f4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Rados=C5=82aw=20Kujawa?= <radoslaw.kujawa@c0ff33.net>
Date: Sun, 29 Jan 2017 11:47:34 +0100
Subject: [PATCH] Add JSR and RTS emulation and tests.

---
 src/65c02isa.csv              |  4 ++--
 src/emulation.c               | 30 ++++++++++++++++++++++++++++++
 test/test_emulation.c         | 22 ++++++++++++++++++++++
 test/test_emulation_jsr_rts.s | 10 ++++++++++
 4 files changed, 64 insertions(+), 2 deletions(-)
 create mode 100644 test/test_emulation_jsr_rts.s

diff --git a/src/65c02isa.csv b/src/65c02isa.csv
index e86bed9..0eac917 100644
--- a/src/65c02isa.csv
+++ b/src/65c02isa.csv
@@ -31,7 +31,7 @@ OP_TRB_ABS,"trb",ABSOLUTE,3,NULL,false
 OP_ORA_ABSX,"ora",ABSOLUTEX,3,emul_ora,false
 OP_ASL_ABSX,"asl",ABSOLUTEX,3,emul_asl,false
 OP_BBR1_REL,"bbr1",ZPR,2,NULL,true
-OP_JSR,"jsr",ABSOLUTE,3,NULL,true
+OP_JSR,"jsr",ABSOLUTE,3,emul_jsr,true
 OP_AND_IZPX,"and",IZPX,2,emul_and,false
 OP_NOPI_23,"nop",IMMEDIATE,2,NULL,false
 OP_NOPI_24,"nop",IMPLIED,1,NULL,false
@@ -95,7 +95,7 @@ OP_NOPI_5D,"nop",ABSOLUTE,3,NULL,false
 OP_EOR_ABSX,"eor",ABSOLUTEX,3,emul_eor,false
 OP_LSR_ABSX,"lsr",ABSOLUTEX,3,emul_lsr,false
 OP_BBR5_REL,"bbr5",ZPR,2,NULL,true
-OP_RTS,"rts",IMPLIED,1,NULL,false
+OP_RTS,"rts",IMPLIED,1,emul_rts,false
 OP_ADC_IZPX,"adc",IZPX,2,NULL,false
 OP_NOPI_63,"nop",IMMEDIATE,2,NULL,false
 OP_NOPI_64,"nop",IMPLIED,1,NULL,false
diff --git a/src/emulation.c b/src/emulation.c
index 5ec5334..8bc4299 100644
--- a/src/emulation.c
+++ b/src/emulation.c
@@ -248,6 +248,24 @@ emul_jmp(rk65c02emu_t *e, void *id, instruction_t *i)
 	e->regs.PC = target;
 }
 
+/* JSR - jump to subroutine */
+void
+emul_jsr(rk65c02emu_t *e, void *id, instruction_t *i)
+{
+	uint16_t jumpaddr; /* addres to jump to */
+	uint16_t retaddr; /* return address */
+
+	jumpaddr = i->op1 + (i->op2 << 8);
+	retaddr = e->regs.PC + 2; /* XXX */
+
+	/* push return address to stack */
+	stack_push(e, retaddr >> 8);
+	stack_push(e, retaddr & 0xFF);
+
+	/* change program counter to point to the new location */
+	e->regs.PC = jumpaddr;
+}
+
 /* LDA - load to accumulator */
 void
 emul_lda(rk65c02emu_t *e, void *id, instruction_t *i)
@@ -376,6 +394,18 @@ emul_ply(rk65c02emu_t *e, void *id, instruction_t *i)
 	e->regs.Y = stack_pop(e);
 }
 
+/* RTS - return from subroutine */
+void
+emul_rts(rk65c02emu_t *e, void *id, instruction_t *i)
+{
+	uint16_t retaddr;
+
+	retaddr = stack_pop(e);
+	retaddr|= stack_pop(e) << 8;
+
+	e->regs.PC = retaddr;
+}
+
 /* RMBx - reset or set memory bit (handles RMB0-RMB7) */
 void
 emul_rmb(rk65c02emu_t *e, void *id, instruction_t *i, uint8_t bit)
diff --git a/test/test_emulation.c b/test/test_emulation.c
index 4dc3a26..f31ef0b 100644
--- a/test/test_emulation.c
+++ b/test/test_emulation.c
@@ -870,6 +870,27 @@ ATF_TC_BODY(emul_jmp, tc)
 	ATF_CHECK(e.regs.PC = 0xC000);
 }
 
+ATF_TC_WITHOUT_HEAD(emul_jsr_rts);
+ATF_TC_BODY(emul_jsr_rts, tc)
+{
+	rk65c02emu_t e;
+	bus_t b;
+
+	b = bus_init();
+	e = rk65c02_init(&b);
+
+	/* JSR and RTS */
+	e.regs.PC = ROM_LOAD_ADDR;
+	ATF_REQUIRE(bus_load_file(&b, ROM_LOAD_ADDR, 
+	    rom_path("test_emulation_jsr_rts.rom", tc)));
+
+	rk65c02_step(&e, 2);
+	ATF_CHECK(e.regs.PC = 0xC006);
+	rk65c02_start(&e); 
+	ATF_CHECK(e.regs.PC = 0xC006);
+
+}
+
 ATF_TP_ADD_TCS(tp)
 {
 	ATF_TP_ADD_TC(tp, emul_and);
@@ -885,6 +906,7 @@ ATF_TP_ADD_TCS(tp)
 	ATF_TP_ADD_TC(tp, emul_inc);
 	ATF_TP_ADD_TC(tp, emul_inx_iny);
 	ATF_TP_ADD_TC(tp, emul_jmp);
+	ATF_TP_ADD_TC(tp, emul_jsr_rts);
 	ATF_TP_ADD_TC(tp, emul_lda);
 	ATF_TP_ADD_TC(tp, emul_nop);
 	ATF_TP_ADD_TC(tp, emul_ora);
diff --git a/test/test_emulation_jsr_rts.s b/test/test_emulation_jsr_rts.s
new file mode 100644
index 0000000..db4de11
--- /dev/null
+++ b/test/test_emulation_jsr_rts.s
@@ -0,0 +1,10 @@
+.org 0xC000
+
+start:	nop
+	jsr foo
+	nop
+	stp
+
+foo:	lda #0xAA
+	rts
+