Zilog Z80 8-Bit Microprocessor

(The following discussion is for informational purposes only. Z80 and the Z80 assembly language are trademarks of ZILOG, Inc.)


The Z80 microprocessor is an 8 bit CPU with a 16 bit address bus capable of direct access of 64k of memory space. It has a language of 252 root instructions and with the reserved 4 bytes as prefixes, acceses an additional 308 instructions. The Z80 was modeled after the 8088 and contains the 78 - 8088 opcodes as a subset to it's language.

Programming features include an accumulator and six eight bit registers that can be paired as 3-16 bit registers. In addition to the general registers, a stack-pointer, program-counter, and two index (memory pointers) registers are provided. While not in the same leauge as the 80486 or 68000 series, the Z80 is extremely useful for low cost control applications. One of the more useful features of the Z80 is the built-in refresh circuitry for ease of design with DRAMs.

The Z80 comes in a 40 pin DIP package. It has been manufactured in A, B, and C models, differing only in maximum clock speed. It also has been manufactured as a stand-alone microcontroler with various configurations of on-chip RAM and EPROM.





     Pin #   Signal (active high unless noted)

      1       A11
      2       A12
      3       A13         {Address bus}
      4       A14
      5       A15
      6       CLK (clock, rising edge trig)
      7       D4
      8       D3
      9       D5          {Data bus}
     10       D6
     11       +5 VDC
     12       D2
     13       D7
     14       D0
     15       D1
     16       INT (Interupt Request)
     17       NMI (Non-maskable Interupt Request)
     18       HALT (Active low)
     19       MREQ (Memory Request, active low)
     20       IORQ (I/O Request, active low)
     21       RD  (Read, active low)
     22       WR  (Write, active low)
     23       BUSAK (Bus Request Acknowloegmnet, active low)
     24       WAIT
     25       BUSRQ (Bus Request)
     26       RESET
     27       MI (Maskable interupt, active low).
     28       REFSH (Refresh timing, active low)
     29       GND
     30       A0
     31       A1
     32       A2
     33       A3
     34       A4
     35       A5
     36       A6
     37       A7
     38       A8
     39       A9
     40       A10


Max. Clock Speed: Z80 - 2.5MHz, Z80A - 4MHz
Power Requirements: Z80 - 5V@60mA, Z80A - 5V@90mA
Operating Temp: 0 - 70 deg C.
Min. Instruction time: 1uS (@4MHz)
Max. Instruction time: 5.75uS (@4MHz)
No. of Instructions: 158 (78 instructions of 8088 are a subset)
Internal Registers: 14
Stack: RAM

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