Zilog Z80

Zilog Z80 is an 8 -bit microprocessor developed by the Zilog Company Inc.. In CMOS technology, the Z80 is available until today.

It was created shortly after Federico Faggin left the company and Intel had founded his own company Zilog. At Intel, he had worked on 8080.

In July 1976, the Z80 was put on the market. It was designed to be binary backwards compatible with the Intel 8080. Thus, most programs ran without modification on it, in particular the CP / M operating system.

Differences for 8080

Compared with the 8080 Z80 has several advantages: A single 5 - V supply voltage instead of 5 V/-5V / 12 V for 8080, a built- refresh control for DRAM, which had to be realized externally otherwise, sophisticated interrupt functions, block copy and comparison instructions ( 16-bit), block IO operations and true 16 -bit registers (IX and IY ), a double set of registers and a lower price.

In addition, the assembly language mnemonics have been simplified: For example, while distinguished the commands for data transport or between internal and external load operations to the Intel 8080, there is the Z80 only the LD command. However, this is not a change in the technology of the processor itself, but only a matter of convention; the assembler for the Z80 generate from the new commands to the same machine code as the 8080 - assembler from the old commands.

Example:

8080 Z80 Code Code Meaning ---------------------------------- MOV A, C LD A, C copies the contents of register C into register STAX B LD (BC ), A copies A register in the address is in register BC LDA 1234 LD A, ( 1234) copies the contents of address 1234 to the register A success

The Z80 quickly outstripped the 8080 and was the most widely used 8 -bit CPU of all time. If one takes into account the absolute size of the market, then he is the most successful since the CPU.

First, the Z80 from Mostek for Zilog was prepared to Zilog own factories had built. Therefore Mostek had a license to market the Z80 under the name MK3880. Later, the Z80 was also made of other semiconductor manufacturers such as NEC under license. Later versions permitted a higher clock rate than the original 2.5 MHz, the 4 MHz offered Z80A, Z80B of 6 MHz and 8 MHz then Z80H. In addition, the power-saving Z80L (L for LowPower ), versions in CMOS technology, which could then be operated even up to 20 MHz emerged.

Other interesting features of this CPU are in undocumented opcodes that further increase the range of commands. Especially the prefix opcode for the IX and IY register can be applied to practically all of the commands that would otherwise be the HL register pair and only relate to the register H or L. Thus, it is possible to use only the upper or lower half of IX and IY is the 8- bit register.

For the construction of microcomputers is a number of peripheral blocks are available. The most important of the Z80 family are PIO (parallel Ein-/Ausgabe ), SIO (serial Ein-/Ausgabe ), CTC ( counters and timers ) and DMA (direct memory access by peripherals).

Use

Initially, the Z80 has been widely used in arcade games, so in Galaxian (1979) and Pac -Man. By 2004, the Neo - Geo machine used it as a sound processor.

In the late 1970s and early 1980s, the Z80 was used in a variety of newly developed home computers, for example in the Tandy TRS 80, NASCOM, video genius, Colour Genie; in the MZ -80 and MZ -700 and 800 - series from Sharp; in Triumph Adler Alphatronic PC; in the Schneider / Amstrad CPC; Amstrad PCW = the cutter " Joyce ", at the Sinclair ZX80, ZX81 and ZX Spectrum; the Commodore C128 ( as a second processor ); in MSX computers and a large number of less well-known business-oriented CP / M machines that dominated the then market like today's Windows PCs. The main competitor of the Z80 in the home computer area was the MOS Technologies 6502, its variants such as the Apple II, Commodore were to find 64 and 8 -bit Ataris.

Many Apple II computers were fitted by means of an expansion card with a Z80 processor to use as CP / M can. Since these Z80 cards were copied in large quantities and operated by unlicensed CP / M- copies, there are no exact figures on their distribution. It should however be in this combination one of the most common CP / M systems.

Later, the processor was also in Texas Instruments calculators (even today Plus, TI -84 Plus and TI -84 Plus Silver Edition or TI- 83) and Sega Master System game consoles used and Game Gear; Sega Mega Drive used it as a coprocessor for audio output. Nintendo Game Consoles Game Boy and Game Boy Color used a Z80 clone ( DMG - CPU), which is manufactured by Sharp. He has a slightly different instruction set.

The Z80 was also popular in embedded systems, where it is still widely used today, for example, works in Toshiba TLCS- 870 series a Z80 core in diverse combinations of memory and peripheral equipment. Also in the produced from 1986 to 1989 in the GDR by VEB AAC Cottbus hybrid synthesizer Tiracon 6V Z80 used for digital control of analog tone generator hardware. However, were used neither the still manufactured in the Soviet Union, the GDR clones of Z80 (see versions).

Another clone of the Z80 is produced by combining the Toshiba TLCS -90 family, a complete microcomputer on a chip, which functions like UART, D and D / A converters, timers, and RAM.

After the advent of more powerful 16- bit CPU, the large amount of existing 8 -bit software was further held (mainly CP / M) with the aid of software emulators can be used.

Even today (2012 ), the Z80 at many universities, among other 8 -bit CPUs like the 8080 or the 6502 model often used as a CPU. At the Technical University of Vienna, he is in the subject " Digital Systems " presented as MC8 ( model computer - 8), wherein the instruction set has been simplified own ASM mnemonics are defined and certain registers, addressing modes and special functions of the CPU are not used to the learning curve to reduce.

Versions

NMOS series:

• " Z80 " ( first series had no number, 2.5 MHz)
• Z8400 ( " Z80 ", 2.5 MHz)
• Z8400A ( " Z80A CPU", 4 MHz)
• Z8400B ( " Z80B CPU", 6 MHz)
• Z8400H ( " Z80H CPU", 8 MHz)
• Z0840004 (4 MHz)
• Z0840006 (6 MHz)
• Z0840008 ( 8 MHz)

CMOS series:

• Z84C0004 (4 MHz)
• Z84C0006 (6 MHz)
• Z84C0008 ( 8 MHz)
• Z84C0010 (10 MHz)
• Z84C0020 (20 MHz)
• Z84C00 - 4PS (4 MHz)

In the GDR, an unlicensed replica of the Z80 under the name of U880 has been developed by a trade embargo. He found wide dissemination through the use of computers in small Robotron and the state-owned enterprise VEB Microelectronics " Wilhelm Pieck " Mühlhausen (KC 85) and in numerous self-made computers ( Z1013 ).

In the Soviet Union also unlicensed replicas ( " Angstrem ", " transistor " ua " Elektronika ", "Integral " ) were under the names T34BM1 and КP1858ВМ1 from different factories to made ​​well into the 1990s. There are known replicas with date codes of 1996.

Successor:

• Z180: From 1985, under the name Hitachi HD64180 microcontroller before, which was very successful mainly due to the integration of numerous peripheral devices. Later, Zilog made ​​the chip as Z180.
• Toshiba combined the Z80 processor and its peripheral devices CTC, SIO and PIO, together with an oscillator and Watchdog function in a 100 - pin package as TMPZ84C015. The component is made ​​to this day, with Zilog as a second manufacturer, name Z84C15.

From Zilog still followed:

• Zilog Z80 Z84C01 code compatible CPU, but different terminal assignment, internal clock generator and control of the HALT behavior
• Z280 16 bit MMU (16 MiB address space) 256 byte cache

Currently are sold:

• EZ80 50 MHz
• EZ80Acclaim! Internal flash and RAM
• EZ80AcclaimPlus! On-chip 10/100BaseT Ethernet MAC

Further, not Z80 compatible CPU types of Zilog:

• Z8 (8 bit)
• Z8000 (16 bits)
• Z80000 (32 bit)