llz80emu is a clock-accurate Zilog Z80 emulator written in C++.
The emulator's behaviour is modeled using information from the following sources:
- Z80 netlist simulation details
- Z80 opcode table
- Z80 flag affection
- Documentation on the undocumented MEMPTR register
- The Undocumented Z80 Documented by Sean Young
- David Bank's documentation on undocumented flag behaviour
To maintain emulation performance and simplicity, the inner operation (ie. during instruction execution) is not accurately modeled; however, the emulator should have the same number of cycles and behaviour for instructions as a real Z80 CPU.
The emulator passes the JSMoo unit test suite, albeit with some instruction timing discrepancies, as well as raddad772's Z80 unit tests to a slightly lesser degree due to instruction timing discrepancies (TODO: check in more detail). The emulator also passes all zexall tests.
The emulator can be compiled using Visual Studio with the provided solution file, as well as with CMake.
llz80emu is provided as a library; ie. a frontend is required to do anything useful with it.
The emulator provides the following publicly accessible methods in the z80emu class:
z80emu::z80emu(bool clk): Instantiate a Z80 emulator object with the specified initial CLK pin state.void z80emu::set_clkpin(bool state): Set the CLK pin state without triggering the CPU's operation.z80_pins_t z80emu::clock(z80_pinbits_t state): Emulate the CPU on a state transition (rising/falling edge) of the CLK pin. Input pins' states are to be provided through thestateargument, and the method returns the new pins' states and directions (seepins.h).void z80emu::trigger_nmi(): Trigger the NMI pin on the CPU. This method is to be called on the falling edge of the NMI pin.z80_pins_t z80emu::get_pins(): Retrieve the emulator's pins' states and directions, without clocking the CPU.z80_registers_t z80emu::get_regs(): Retrieve the emulator's register values.void z80emu::set_regs(const z80_registers_t& regs): Set the emulator's register values.
Pull requests and discussions/bug reports through Issues are welcome.