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diagnostics\n\nIn Z80 assembly, NOP (No Operation) is the opcode 0x00.\n\nWhen executed, the CPU does nothing for one machine cycle and then increments the program counter (PC) to fetch the next instruction.\n\n## What it Tests\n* Clock circuit (CPU is being driven)\n* Reset circuit (PC starts at 0x0000)\n* Address bus (sequential counting)\n* Basic instruction fetch and decode mechanism\n\n\n## What You Can See\n* A display of the address bus contents as it increments\n* Status of RFSH, M1, MREQ and RD signals\n\n## What You Can Measure\n* Test points for clock, 0V and 5V\n* Test points for s RFSH, M1, MREQ, RD IORQ, WR, HALT, BUSACK (Useful if your Z80 is mis-behaving)\n\n\n# Z80 NOP HALT Tester v2.1\n\nZ80 CPU NOP HALT Instruction Tester\n\n## Introduction\n\nAn extended version of the board which allows the use of HALT instructions to test dynamic memory refresh operations\n\nIn Z80 assembly, HALT is the opcode 0x76.\n\nWhen executed, the CPU enters HALT mode and ceases executing except for memory refresh operations\n\n## Documentation\n\nFor full documentation, see the [NOP pdf here](Z80_NOP.pdf) and [NOP HALT pdf here](Z80_NOP_HALT.pdf)\n\n## Release 1.2 Boards\n\n![PCB From JLCPCB](pcb.png)\n\n![Model](3d_pcb.png)\n\n![Built PCB](built_pcb.png)\n","project_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fcodesqueak%2Fz80_nop","html_url":"https://awesome.ecosyste.ms/projects/github.com%2Fcodesqueak%2Fz80_nop","lists_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fcodesqueak%2Fz80_nop/lists"}