Merge 0f1c01ce60 into 4847744518

src/cpu.rs

@@ -156,7 +156,7 @@ impl<M: Bus, V: Variant> CPU<M, V> {
                         // (Output: a 16-bit address)
                         // TODO: If the pointer ends in 0xff, then incrementing it would propagate
                         // the carry to the high byte of the pointer. This incurs a cost of one
-                        // machine on the real 65C02, which is not implemented here.
+                        // machine cycle on the real 65C02, which is not implemented here.
                         let slice = read_address(memory, address_from_bytes(slice[0], slice[1]));
                         OpInput::UseAddress(address_from_bytes(slice[0], slice[1]))
                     }
@@ -580,6 +580,9 @@ impl<M: Bus, V: Variant> CPU<M, V> {
             (Instruction::STY, OpInput::UseAddress(addr)) => {
                 self.memory.set_byte(addr, self.registers.index_y);
             }
+            (Instruction::STZ, OpInput::UseAddress(addr)) => {
+                self.memory.set_byte(addr, 0);
+            }
 
             (Instruction::TAX, OpInput::UseImplied) => {
                 let val = self.registers.accumulator;

src/instruction.rs

@@ -100,6 +100,7 @@ pub enum Instruction {
     STA,   // STore Accumulator............. | .. .....            M = A
     STX,   // STore X register.............. | .. .....            M = X
     STY,   // STore Y register.............. | .. .....            M = Y
+    STZ,   // STore Zero.................... | .. .....            M = Y
     TAX,   // Transfer Accumulator to X..... | N. ...Z.   X          = A
     TAY,   // Transfer Accumulator to Y..... | N. ...Z.     Y        = A
     TSX,   // Transfer Stack pointer to X... | N. ...Z.   X          = S
@@ -494,6 +495,10 @@ impl crate::Variant for Cmos6502 {
             0x3a => Some((Instruction::DEC, AddressingMode::Accumulator)),
             0x6c => Some((Instruction::JMP, AddressingMode::Indirect)),
             0x80 => Some((Instruction::BRA, AddressingMode::Relative)),
+            0x64 => Some((Instruction::STZ, AddressingMode::ZeroPage)),
+            0x74 => Some((Instruction::STZ, AddressingMode::ZeroPageX)),
+            0x9c => Some((Instruction::STZ, AddressingMode::Absolute)),
+            0x9e => Some((Instruction::STZ, AddressingMode::AbsoluteX)),
             _ => Nmos6502::decode(opcode),
         }
     }