From b31d7490b2d318d742cdd20a44003655cc565613 Mon Sep 17 00:00:00 2001
From: Byron Lathi <byron@byronlathi.com>
Date: Sun, 26 Apr 2026 22:13:42 -0700
Subject: [PATCH] Add indirect jump

---
 sim/verilog6502_32bit_test.py | 53 ++++++++++++++++++++++++++++++++---
 src/cpu_65c02.v               | 19 +++++++++----
 2 files changed, 63 insertions(+), 9 deletions(-)

diff --git a/sim/verilog6502_32bit_test.py b/sim/verilog6502_32bit_test.py
index 02332cd..575c7df 100644
--- a/sim/verilog6502_32bit_test.py
+++ b/sim/verilog6502_32bit_test.py
@@ -287,10 +287,55 @@ async def test_absolute_x_indirect(dut):
         (0x00000205, False, None),            # addr 2
         (0x00000206, False, None),            # addr 3
         (0xdeadbef0, False, None),            # addr 0
-        (0xdeadbef1, False, None),            # addr 0
-        (0xdeadbef2, False, None),            # addr 0
-        (0xdeadbef3, False, None),            # addr 0
-        (0xbeefb055, False, None),            # 
+        (0xdeadbef1, False, None),            # addr 1
+        (0xdeadbef2, False, None),            # addr 2
+        (0xdeadbef3, False, None),            # addr 3
+        (0xbeefb055, False, None),            # target
+    ]
+
+    await check_instruction_sequence(dut, expected_cpu_outputs)
+
+
+@cocotb.test
+async def test_indirect(dut):
+    cocotb.start_soon(Clock(dut.clk, CLK_PERIOD, unit="ns").start())
+    cocotb.start_soon(handle_memory(dut))
+
+    write_dword(0xfffffff4, 0x200)
+
+    # jmp ($deadbeef)
+    write_bytes(0x200, [0x6c, 0xef, 0xbe, 0xad, 0xde])
+    write_byte(0xbeefb055, 0xcb)
+
+    write_dword(0xdeadbeef, 0xbeefb055)
+
+    dut.RDY.value = Immediate(1)
+
+    dut.reset.value = Immediate(1)
+    for _ in range(10):
+        await RisingEdge(dut.clk)
+    dut.reset.value = 0
+
+    expected_cpu_outputs = [
+        None,   # ignore reset sequence
+        None,
+        None,
+        None,
+        None,
+        None,
+        None,
+        None,
+        None,
+        (0x00000200, False, None),            # jmp ($deadbeef)
+        (0x00000201, False, None),            # addr 0
+        (0x00000202, False, None),            # addr 1
+        (0x00000203, False, None),            # addr 2
+        (0x00000204, False, None),            # addr 3
+        (0xdeadbeef, False, None),            # addr 0
+        (0xdeadbef0, False, None),            # addr 1
+        (0xdeadbef1, False, None),            # addr 2
+        (0xdeadbef2, False, None),            # addr 3
+        (0xbeefb055, False, None),            # target
     ]
 
     await check_instruction_sequence(dut, expected_cpu_outputs)
diff --git a/src/cpu_65c02.v b/src/cpu_65c02.v
index a1a890c..de8b6bd 100644
--- a/src/cpu_65c02.v
+++ b/src/cpu_65c02.v
@@ -134,7 +134,7 @@ wire [7:0] P = { N, V, 2'b11, D, I, Z, C };
  * instruction decoder/sequencer
  */
 
-reg [5:0] state;
+reg [6:0] state;
 
 /*
  * control signals
@@ -272,7 +272,9 @@ parameter
     ABSX3  = 7'd61, // TODO
     ABSX4  = 7'd62, // TODO
     JMPIX3 = 7'd63, // TODO
-    JMPIX4 = 7'd64; // TODO
+    JMPIX4 = 7'd64, // TODO
+    JMPI2  = 7'd65, // TODO
+    JMPI3  = 7'd66; // TODO
 
 `ifdef SIM
 
@@ -342,6 +344,8 @@ always @*
             JMP3:   statename = "JMP3";
             JMPI0:  statename = "JMPI0";
             JMPI1:  statename = "JMPI1";
+            JMPI2:  statename = "JMPI2";
+            JMPI3:  statename = "JMPI3";
             JMPIX0: statename = "JMPIX0";
             JMPIX1: statename = "JMPIX1";
             JMPIX2: statename = "JMPIX2";
@@ -371,7 +375,7 @@ always @*
 
 
         JMP3,
-        JMPI1,
+        JMPI3,
         JMPIX3,
         JSR3,
         RTS3,
@@ -412,7 +416,10 @@ always @*
         BRA0,
         BRA2,
         BRK5,
+        JMPI0,
         JMPI1,
+        JMPI2,
+        JMPI3,
         JMP0,
         JMP1,
         JMP2,
@@ -449,7 +456,7 @@ always @*
         INDX3,
         INDY2,
         JMP3,
-        JMPI1,
+        JMPI3,
         RTI4,
         ABS3:           AB = { DIMUX, ADD, alu_sr_0, alu_sr_1};
 
@@ -1123,7 +1130,9 @@ always @(posedge clk or posedge reset)
         JMP3    : state <= DECODE;
 
         JMPI0   : state <= JMPI1;
-        JMPI1   : state <= JMP0;
+        JMPI1   : state <= JMPI2;
+        JMPI2   : state <= JMPI3;
+        JMPI3   : state <= JMP0;
 
         BRK0    : state <= BRK1;
         BRK1    : state <= BRK2;