Add RTI

sim/verilog6502_32bit_test.py

@@ -539,7 +539,73 @@ async def test_jsr(dut):
 
     await check_instruction_sequence(dut, expected_cpu_outputs)
 
-# @cocotb.test
+@cocotb.test
+async def test_rti(dut):
+    cocotb.start_soon(Clock(dut.clk, CLK_PERIOD, unit="ns").start())
+    cocotb.start_soon(handle_memory(dut))
+
+    write_dword(0xfffffff4, 0x200)
+    write_dword(0xfffffffc, 0x300)
+
+
+    # @0x200
+    # ldx #$ff
+    # txs
+    # brk
+    # wai
+    # @0x300
+    # rti
+
+    write_bytes(0x200, [0xa2, 0xff, 0x9a, 0x00, 0x00, 0xcb]) # BRK is technically a 2 byte instruction
+    write_bytes(0x300, [0x40])
+
+    dut.RDY.value = Immediate(1)
+
+    dut.reset.value = Immediate(1)
+    for _ in range(10):
+        await RisingEdge(dut.clk)
+    dut.reset.value = 0
+
+    expected_cpu_outputs = [
+        None,   # ignore reset sequence
+        None,
+        None,
+        None,
+        None,
+        None,
+        None,
+        None,
+        None,
+        (0x00000200, False, None),  # ldx #$ff
+        (0x00000201, False, None),  # immediate
+        (0x00000202, False, None),  # txs
+        (0x00000203, False, None),  # txs
+        (0x00000203, False, None),  # brk
+        (0x00000204, False, None),  # brk
+        (0x000001ff, True,  0x00),  # brk   31-24
+        (0x000001fe, True,  0x00),  # brk   13-16
+        (0x000001fd, True,  0x02),  # brk   15-08
+        (0x000001fc, True,  0x05),  # brk   07-00
+        (0x000001fb, True,  0xb4),  # brk   flags
+        (0xfffffffc, False, None),  # vector
+        (0xfffffffd, False, None),  # vector
+        (0xfffffffe, False, None),  # vector
+        (0xffffffff, False, None),  # vector 
+        (0x00000300, False, None),  # rti
+        (0x00000301, False, None),  # rti
+        (0x000001fa, False, None),  # rti
+        (0x000001fb, False, None),  # rti
+        (0x000001fc, False, None),  # rti
+        (0x000001fd, False, None),  # rti
+        (0x000001fe, False, None),  # rti
+        (0x000001ff, False, None),  # rti
+        (0x00000205, False, None),  # wai
+    ]
+
+    await check_instruction_sequence(dut, expected_cpu_outputs)
+
+
+@cocotb.test
 async def test_adc(dut):
     cocotb.start_soon(Clock(dut.clk, CLK_PERIOD, unit="ns").start())
     cocotb.start_soon(handle_memory(dut))

src/cpu_65c02.v

@@ -257,7 +257,7 @@ parameter
     RTI1   = 7'd38, // RTI     - read P from stack
     RTI2   = 7'd39, // RTI     - read PCL from stack
     RTI3   = 7'd40, // RTI     - read PCH from stack
-    RTI4   = 7'd41, // RTI     - read PCH from stack
+    RTI6   = 7'd41, // RTI     - read PCH from stack
     RTS0   = 7'd42, // RTS     - send S to ALU (+1)
     RTS1   = 7'd43, // RTS     - read PCL from stack
     RTS2   = 7'd44, // RTS     - write PCL to ALU, read PCH
@@ -292,7 +292,9 @@ parameter
     JSR6   = 7'd74,
     JSR7   = 7'd75,
     RTS3   = 7'd76,
-    RTS4   = 7'd77;
+    RTS4   = 7'd77,
+    RTI4   = 7'd78,
+    RTI5   = 7'd79;
 
 
 `ifdef SIM
@@ -352,6 +354,8 @@ always @*
             RTI2:   statename = "RTI2";
             RTI3:   statename = "RTI3";
             RTI4:   statename = "RTI4";
+            RTI5:   statename = "RTI5";
+            RTI6:   statename = "RTI6";
             RTS0:   statename = "RTS0";
             RTS1:   statename = "RTS1";
             RTS2:   statename = "RTS2";
@@ -406,10 +410,10 @@ always @*
         JMP3,
         JMPI3,
         JMPIX3,
-        JSR7:           PC_temp = { DIMUX, ADD, alu_sr_0, alu_sr_1};
+        JSR7,
+        RTI6:           PC_temp = { DIMUX, ADD, alu_sr_0, alu_sr_1};
 
-        RTS5,
+        RTS5:           PC_temp = { DIMUX, ADD, alu_sr_0, alu_sr_1} + 2;
-        RTI4:           PC_temp = { DIMUX, ADD, alu_sr_0, alu_sr_1} + 2;
 
 
         BRA1:           PC_temp = { ABR[15:8], ADD };
@@ -459,7 +463,7 @@ always @*
         JSR4,
         JSR5,
         JSR6,
-        RTI4,
+        RTI6,
         RTS3,
         RTS4,
         RTS5:           PC_inc = 1;
@@ -493,7 +497,7 @@ always @*
         INDX5,
         JMP3,
         JMPI3,
-        RTI4,
+        RTI6,
         ABS3:           AB = { DIMUX, ADD, alu_sr_0, alu_sr_1};
 
         BRA2,
@@ -520,6 +524,8 @@ always @*
         RTI1,
         RTI2,
         RTI3,
+        RTI4,
+        RTI5,
         BRK2,           
         BRK3,
         BRK4:           AB = { 16'h0, STACKPAGE, ADD };
@@ -644,7 +650,7 @@ always @*
 
         PULL1,
          RTS4,
-         RTI3,
+         RTI5,
          BRK5,
          JSR0,
          JSR4 : write_register = 1;
@@ -740,7 +746,7 @@ always @*
         PULL1,
         PUSH1,
         RTI0,
-        RTI3,
+        RTI5,
         RTS0,
         RTS4   : regsel = SEL_S;
 
@@ -780,7 +786,9 @@ end
 always @* begin
     case ( state )
         RTS2,
-        RTS3:       sr_sel = SR_DI;
+        RTS3,
+        RTI3,
+        RTI4:       sr_sel = SR_DI;
 
         default:    sr_sel = SR_ALU;
     endcase
@@ -788,7 +796,8 @@ end
 
 always @*begin
     case ( state)
-        RTS4:       alu_sr_enable = 0;
+        RTS4,
+        RTI5:       alu_sr_enable = 0;
         default:    alu_sr_enable = 1;
     endcase
 end
@@ -855,6 +864,8 @@ always @*
         RTS3,
         RTI1,
         RTI2,
+        RTI3,
+        RTI4,
         BRK1,
         BRK2,
         BRK3,
@@ -904,6 +915,8 @@ always @*
          RTI0,
          RTI1,
          RTI2,
+         RTI3,
+         RTI4,
          REG,
          JSR0,
          JSR1,
@@ -913,6 +926,8 @@ always @*
          BRK0,
          BRK1,
          BRK2,
+         BRK3,
+         BRK4,
          PUSH0,
          PUSH1,
          PULL0,
@@ -956,6 +971,8 @@ always @*
         RTI0,
         RTI1,
         RTI2,
+        RTI3,
+        RTI4,
         RTS0,
         RTS1,
         RTS2,
@@ -1219,7 +1236,9 @@ always @(posedge clk or posedge reset)
         RTI1    : state <= RTI2;
         RTI2    : state <= RTI3;
         RTI3    : state <= RTI4;
-        RTI4    : state <= DECODE;
+        RTI4    : state <= RTI5;
+        RTI5    : state <= RTI6;
+        RTI6    : state <= DECODE;
 
         RTS0    : state <= RTS1;
         RTS1    : state <= RTS2;
@@ -1268,7 +1287,7 @@ always @(posedge clk or posedge reset)
         REG,
         PUSH1,
         PULL2,
-        RTI4,
+        RTI6,
         JMP3,
         BRA2   : SYNC <= 1'b1;
         default: SYNC <= 1'b0;