Z80 instruction register The refresh counter is increased by 1 after every instruction opcode fetch, and after the instruction opcode has been fetched and being decoded, the idle time on the bus is used to do a refresh bus cycle with the register Jun 27, 2021 · I have an emulator running on macOS. Aug 18, 2022 · Z80 registers are specialized. Having recently found out about that, I find myself curious how much circuitry would have been needed to allow the inc/dec to add or subtract 256 rather than 1, and use that to expedite the s8+16 arithmetic used in "jr" or the indexed addressing modes. *3 - While the 6502 did not feature a halt instruction (not until the 65C02), Atari's TIA for the VCS did implement hardware to make the CPU go into a forced halt state when accessing certain addresses much like a 'Wait for Line'-Halt instruction. What should I have a look at? Jan 10, 2018 · The Z80 was one of the most popular CPUs of the seventies and eighties. I used it for PS/2 keyboard and USB connection to my breadboard Z80 computer running at 2. Inherited Basics Most of this is inherited straight from the 8080: A - General purpose accumulator HL - Primary memory pointer DE - Secondary memory pointer (XCHG / EX HL,DE) DE / BC - Ìndex pointer (STAX, LDAX) H, D and B are always the higher byte of any Oct 26, 2016 · The Zilog Z80 microprocessor, known for its use in the ZX Spectrum, was designed to be a backwards-compatible extension to the Intel 8080 processor. Much like A, X and Y have different features on a 6502. Mar 21, 2019 · It's a part of standard Z80 family chips and has two channels. Z84C40 can divide system clock by factor of 16, 32 or 64 thus I run my UART-USB bridge at 38,400 baud without use of 4-bit counter as system clock divider. y1 mtwy wlw amcnrv my6n 8ukx xd1afd f1j ndbzut p1dtytbbj