![]() ![]() Note: The unused (-) opcodes will lock up the Game Boy CPU when used. Moved, Removed, and Added Opcodes Opcode Z80 GMB The Game Boy operates approximately as fast as a 4 MHz Z80 (8 MHz in CGB double speed mode), with execution time of all instructions having been rounded up to a multiple of 4 cycles. Block commands are gone, but autoincrementing HL accesses are added. IN/OUT (C) are replaced with new LD ($FF00+C) opcodes. That means 16bit memory accesses are mostly missing, 16bit arithmetic functions are heavily cut-down, and some other missing commands. That means no IX- or IY-registers.Īll ED-prefixed instructions are missing. In addition to the removed 8080 instructions, the other exchange instructions have been removed (including total absence of second register set).Īll DD- and FD-prefixed instructions are missing. OK Last test :-) 4 years ago TV80-verilog Verilog code moved to TV80-verilog folder 4 years ago Tinybasic Tinybasic added. So have EX (SP),HL (XTHL) and EX DE,HL (XCHG). GitHub - Obijuan/Z80-FPGA: Z80 CPU for OpenFPGAs, with Icestudio Obijuan Z80-FPGA master 1 branch 5 tags Code 177 commits Instruction-exerciser Test 67: stabd. The sign and parity/overflow flags have been removed, as have the 12 RET, CALL, and JP instructions conditioned on them. Instead, I/O ports are accessed directly by normal LD instructions, or by new LD (FF00+n) opcodes. ![]() Unlike the 8080 and Z80, the Game Boy has no dedicated I/O bus and no IN/OUT opcodes. Also, all known Game Boy assemblers use the more obvious Z80-style syntax, rather than the chaotic 8080-style syntax. It is missing a handful of 8080 instructions but does support JR and almost all CB-prefixed instructions. The processor uses 16-bit addresses to access these bytes, so there can be anything up to 64k (65536) bytes of memory. These bytes contain both the program that the processor is executing and the data items that the program is working on. The Game Boy CPU has a bit more in common with an older Intel 8080 CPU than the more powerful Zilog Z80 CPU. The Z80 uses 8-bit bytes which are stored in memory. Using CP/M Commands and the CCP Programming with BDOS The BIOS interface. Background History of CP/M Architecture of CP/M. Please go to to read Pan Docs or to to contribute.Ĭlick here to go to this section of Pan Docs in the new location: Comparison with 8080 The Z80 Microprocessor Navigation Home email. Pan Docs is now officially hosted on gbdev.io as a living document. The copy of Pan Docs hosted on this wiki is considered deprecated. ![]()
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