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Zilog's Z80 8-Bit Microprocessor


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 8080 and contains the 78 - 8080 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*.

Other Device Numbers

Pin-Out and Signal Description

Pin # Signal (active high unless noted) comment
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 +5V
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
25 BUSRQ Bus Request
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

Device Specifications

Max. Clock Speed Z80 - 2.5MHz, Z80A - 4MHz
Power Requirements Z80 - 60mA, Z80A - 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 8080 are a subset)
Internal Registers 14
Stack RAM


This information was compiled by Robert Wenzlaff with small corrections by me.

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