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One of the first Z80 microprocessors manufactured; the date stamp is from June 1976.
A CMOS Z80 in a QFP package.

The Zilog Z80 is an 8-bit microprocessor designed and sold by Zilog from July 1976 onwards. It was widely used both in desktop and embedded computer designs as well as for military purposes. The Z80 and its derivatives and clones make up one of the most commonly used CPU families of all time, and, along with the MOS Technology 6502 family, dominated the 8-bit microcomputer market from the late 1970s to the mid-1980s.

Although Zilog made early attempts with advanced mini-computer like versions of the Z80-architecture (Z800 and Z280), these chips never caught on. The company was also trying hard in the workstation market with its Z8000 and 32-bit Z80000 (both unrelated to Z80). In recent decades Zilog has refocused on the ever-growing market for embedded systems (for which the original Z80 and the Z180 were designed) and the most recent Z80-compatible microcontroller family, the fully pipelined 24-bit eZ80 with a linear 16 MB address range, has been successfully introduced alongside the simpler Z180 and Z80 products.

Zilog licensed the Z80 core to any company wishing to make the device royalty free, though many East European and Russian manufacturers made unlicensed copies. This enabled a small company's product to gain acceptance in the world market since second sources from far larger companies such as Toshiba started to manufacture the device. Consequently Zilog has made less than 50% of the Z80s since its conception.


Brief history and overview

The Z80 came about when Federico Faggin, after working on the 8080, left Intel at the end of 1974 to found Zilog with Ralph Ungermann, and by July 1976 they had the Z80 on the market.[1] It was designed to be binary compatible with the Intel 8080[2][3] so that most 8080 code, notably the CP/M operating system, would run unmodified on it. Masatoshi Shima, co-designer of the 4004 and the 8080 also contributed to the development of the Z80.[4]

The Z80's original DIL40 chip package pinout.

The Z80 offered many real improvements over the 8080:[3]

  • An enhanced instruction set[5] including bit manipulation, block move, block I/O, and byte search instructions[6]
  • New IX and IY index registers and instructions for them
  • A more automatic and general vectorized interrupt system, mode 2, as well as a fixed vector interrupt system, mode 1, for simple systems with minimal hardware (mode 0 being the 8080-compatible mode).[7]
  • Two separate register files, which could be quickly switched, to speed up response to interrupts
  • Less hardware required for power supply, clock generation and interface to memory and I/O
    • Single 5 Volt power supply (the 8080 needed -5V/+5V/+12V)
    • Single-phase 5V clock (the 8080 needed a two-phase high-amplitude clock generator)
    • A built-in DRAM refresh mechanism that would otherwise have to be provided by external circuitry
    • Non-multiplexed buses (the 8080 had state-signals multiplexed onto the data bus)
  • A much lower price

The Z80 took over from the 8080 and its offspring, the 8085, in the processor market,[8] and became one of the most popular 8-bit CPUs.[9][10] Perhaps a key to the initial success of the Z80 was the built-in DRAM refresh, and other features which allowed systems to be built with fewer support chips (later on, most Z80 systems have been embedded systems, which typically uses static RAM and hence does not need this refresh).

For the original NMOS design, the specified upper clock frequency limit increased successively from the introductory 2.5 MHz, via the well known 4 MHz (Z80A), up to 6 (Z80B) and 8 MHz (Z80H).[11][12] A CMOS version was also developed with specified frequency limits[13] ranging from 4 MHz up to 20 MHz for the version sold today. The CMOS version also allowed a low-power sleep with internal state retained (having no lower frequency limit).[14] The fully compatible derivatives HD64180/Z180[15][16] and eZ80 are currently specified for up to 33 and 50 MHz respectively.

Technical description


Programming model and register set

The programming model and register set are conventional and similar to the related x86 family. The 8080 compatible registers AF, BC, DE, HL are duplicated as two separate banks in the Z80,[17] where the processor can quickly switch from one bank to the other[18]; a feature useful for speeding up responses to single level, high priority interrupts. This feature was present in the Datapoint 2200 but was not implemented by Intel in the 8008. The dual-register set makes sense as the Z80 (like most microprocessors at the time) was really intended for embedded use, not for personal computers, or the yet-to-be invented home computers.[19] It also turned out to be quite useful for heavily optimized manual assembly coding. Some software, especially games for the MSX, Sinclair ZX Spectrum and other Z80 based computers took Z80 assembly optimization to rather extreme levels, employing the duplicated registers among other things.

The Z80 architecture.

Like on the 8080, 8-bit registers are typically coupled to provide 16-bit versions. The 8080 compatible registers are:

  • AF - 8-bit accumulator (A) and flag bits (F) carry, zero, minus, parity/overflow, half-carry (used for BCD), and an Add/Subtract flag (usually called N) also for BCD
  • BC - 16-bit data/address register or two 8-bit registers
  • DE - 16-bit data/address register or two 8-bit registers
  • HL - 16-bit accumulator/address register or two 8-bit registers
  • SP - stack pointer, 16 bits
  • PC - program counter, 16 bits

The new registers introduced with the Z80 are:

  • IX - 16-bit index or base register for 8-bit immediate offsets
  • IY - 16-bit index or base register for 8-bit immediate offsets
  • I - interrupt vector base register, 8 bits
  • R - DRAM refresh counter, 8 bits (msb does not count)
  • AF' - alternate (or shadow) accumulator and flags (toggled in and out with EX AF,AF' )
  • BC', DE', and HL' - alternate (or shadow) registers (toggled in and out with EXX)
  • Four bits of interrupt status and interrupt mode status

There is no direct access to the alternate registers; instead, two special instructions, EX AF,AF' and EXX[20], each toggles one of two multiplexer flip-flops; this enables fast context switches for interrupt service routines: EX AF, AF' may be used alone (for really simple and fast interrupt routines) or together with EXX to swap the whole AF, BC, DE, HL set; still much faster than pushing the same registers on the stack (slower, lower priority, or multi level interrupts normally use the stack to store registers).

The refresh register, R, increments[21] each time the CPU fetches an opcode (or opcode prefix) and has therefore no simple relationship with program execution. This has sometimes been used to generate pseudorandom numbers in games, and also in software protection schemes. It has also been employed as a "hardware" counter in some designs; a famous example of this is the ZX81, which lets it keep track of character positions on the TV screen by triggering an interrupt at wrap around (by connecting INT to A6).

The interrupt vector register, I, is used for the Z80 specific mode 2 interrupts (selected by the IM 2 instruction). It supplies the base address for a 128-entry table of service routine addresses which are selected via a pointer sent to the CPU during an interrupt acknowledge cycle.[7] The pointer identifies a particular peripheral chip and/or peripheral function or event, where the chips are normally connected in a so called daisy-chain for priority resolution. Like the refresh register, this register has also sometimes been used creatively.

The Z80 assembly language

Background - the Datapoint 2200 and Intel 8008

The first Intel 8008 assembly language was based on a very simple (but systematic) syntax inherited from the Datapoint 2200 design. This original syntax was later transformed into a new, somewhat more traditional, assembly language form for this same original 8008 chip. At about the same time, the new assembly language was also extended to accommodate the added addressing possibilities in the more advanced Intel 8080 chip (the 8008 and 8080 shared a language subset without being binary compatible; the 8008 actually was binary compatible with the Datapoint 2200 however).

In this process, the mnemonic L, for LOAD, was replaced by various abbreviations of the words LOAD, STORE and MOVE, intermixed with other symbolic letters. The mnemonic letter M, for memory (referenced by HL), was lifted out from within the instruction mnemonic to become a syntactically freestanding operand, while registers and combinations of registers became very inconsistently denoted; either by abbreviated operands (MVI D, LXI H etc), within the instruction mnemonic itself (LDA, LHLD etc), or both at the same time (LDAX B, STAX D etc).

Datapoint 2200

& i8008

i8080 Z80 i8086/i8088
ca -1973 ca 1974 1976 1978
LDI 56 MVI D,56 LD D,56 MOV DL,56
LMI 56 MVI M,56 LD (HL),56 MOV byte ptr [BP],56
-- LDA 1234 LD A,(1234) MOV AL,[1234]
-- STA 1234 LD (1234),A MOV [1234],AL
-- -- LD B,(IX+56) MOV BL,[SI+56]
-- -- LD (IX+56),C MOV [SI+56],CL
-- -- LD (IY+56),78 MOV byte ptr [DI+56],78
-- LXI B,1234 LD BC,1234 MOV BX,1234
-- LXI H,1234 LD HL,1234 MOV BP,1234
-- SHLD 1234 LD (1234),HL MOV [1234],BP
-- LHLD 1234 LD HL,(1234) MOV BP,[1234]
-- -- LD BC,(1234) MOV BX,[1234]
-- -- LD IX,(1234) MOV SI,[1234]


Illustration of four syntaxes, using samples of equivalent, or (for 8086) very similar, load and store instructions.

The new syntax

Intel had claimed copyright on their assembly mnemonics. Yet another assembly syntax was therefore developed, but this time with a more systematic approach:

  • All registers and register pairs are explicitly denoted by their full names
  • Round brackets are consistently used to indicate "memory contents at" (indirection, or pointer dereferencing) with the exception of some jump instructions.[23].
  • All load and store instructions use the same mnemonic name, LD, for LOAD (a return to the simplistic Datapoint 2200 vocabulary); other common instructions, such as ADD, INC etc, use the same mnemonic regardless of addressing mode or operand size. This is possible because the operands themselves carry enough information.

These principles made it straightforward to find names and forms for all new Z80 instructions, as well as orthogonalizations of old ones, such as LD BC,(1234) above.

It is interesting to see the resemblance between Z80 and 8086 syntax, as illustrated by the table. Apart from naming differences, and despite a certain discrepancy in basic register structure, the two are virtually isomorphous for a large portion of instructions. Whether this is due to some common influence on both design teams (above 8080, such as PDP-11), the competitive nature of the relation between the two designs, or maybe just a matter of taste, is, so far, uncertain.[24]

Instruction set and encoding

The Z80 uses 252 out of the available 256 codes as single byte opcodes ("root instruction"); the four remaining codes are used extensively as opcode prefixes:[25] CB and ED enable extra instructions and DD or FD selects IX+d or IY+d respectively (in some cases without displacement d) in place of HL. This scheme gives the Z80 a large number of permutations of instructions and registers; ZiLOG categorizes these into 158 different "instruction types", 78 of which are the same as those of the Intel 8080[25] (allowing operation of 8080 programs on a Z80). The ZiLOG documentation further groups instructions into the following categories:

  • 8-bit arithmetic and logic operations
  • 16-bit arithmetic
  • 8-bit load
  • 16-bit load
  • Bit set, reset, and test
  • Call, return, and restart
  • Exchange, block transfer, and search
  • General purpose arithmetic and CPU control
  • Input and output
  • Jump
  • Rotate and shift

No multiply instruction is available in the original Z80.[26] Different sizes and variants of additions, shifts, and rotates have somewhat differing effects on flags because the flag-influencing properties of the 8080 were copied. Load instructions do not affect the flags (except for the special purpose I and R register loads). The index register instructions are useful for reducing code size, and, while some of them are not much faster than "equivalent" sequences of simpler operations, they also save execution time indirectly by reducing the need to save and restore registers.[27] Similarly, instructions for 16-bit additions are not particularly fast (11 clocks) in the original Z80; nonetheless, they are about twice as fast as performing the same calculations using 8-bit operations, and equally important, they reduce register usage.

Undocumented instructions

The index registers, IX and IY, were intended as flexible 16 bit pointers, enhancing the ability to manipulate memory, stack frames and data structures. Officially, they were treated as 16 bit only. In reality, they were implemented as a pair of 8 bit pair registers,[28] in the same fashion as the HL register, which is accessible either as 16 bits or separately as the High and Low registers. Even the binary opcodes (machine language) were identical, but preceded by a new opcode prefix.[29] ZiLOG published the opcodes and related mnemonics for the intended functions, but did not document the fact that every opcode that allowed manipulation of the H and L registers was equally valid for the 8 bit portions of the IX and IY registers. As an example, the opcode 26h followed by an immediate byte value (LD H,n) will load that value into the H register. Preceding this two-byte instruction with the IX register's opcode prefix DD, would instead result in the most significant 8 bits of the IX register being loaded with that same value. A notable exception to this would be instructions similar to LD H,(IX+d) which make use of both the HL and IX or IY registers in the same instruction;[29] in this case the DD prefix is only applied to the (IX+d) portion of the instruction.

There are several other undocumented instructions as well.[30]

Instruction execution

Each instruction is executed in steps that are usually termed machine cycles (M-cycles), each of which can take between one and six clock periods (T-cycles).[31] Each M-cycle corresponds roughly to one memory access and/or internal operation. Many instructions actually end during the M1 of the next instruction which is known as a fetch/execute overlap.

Examples of typical instructions (R=read, W=write)



instruction M1 M2 M3 M4 M5 M6
1[32] INC BC opcode
2[33] ADD A,n opcode n
3[34] ADD HL,DE opcode internal internal
4[35] SET b,(HL) prefix opcode R(HL), set W(HL)
5[36] LD (IX+d),n prefix opcode d n,add W(IX+d)
6[37] INC (IY+d) prefix opcode d add R(IY+d),inc W(IY+d)

The Z80 machine cycles are sequenced by an internal state machine which builds each M-cycle out of 3,4,5 or 6 T-cycles depending on context. This avoids cumbersome asynchronous logic and makes the control signals behave consistently at a wide range of clock frequencies. Naturally, it also means that a higher frequency crystal must be used than without this subdivision of machine cycles (approximately 2-3 times higher). It does not imply tighter requirements on memory access times, however, as a high resolution clock allows more precise control of memory timings and memory therefore can be active in parallel with the CPU to a greater extent (i.e. sitting less idle), allowing more efficient use of available memory performance. For instruction execution, the Z80 combines two full clock cycles into a long memory access period (the M1-signal) which would typically last only a fraction of a (longer) clock cycle in a more asynchronous design (such as the 6800, or similar).

Memory, especially EPROM, but also Flash, were generally slow as compared to the state machine sub-cycles (clock cycles) used in contemporary microprocessors. The shortest machine cycle that could safely be used in embedded designs has therefore often been limited by memory access times, not by the maximum CPU frequency (especially so during the home computer era). However, this relation has slowly changed during the last decades, particularly regarding SRAM; cacheless single cycle designs such as the eZ80 have therefore become much more meaningful recently.

Compatible peripherals

Zilog introduced a number of peripheral parts for the Z80, which all supported the Z80's interrupt handling system and I/O address space. These included the CTC (Counter-Timer-Circuit), the SIO (Serial Input Output), the DMA (Direct Memory Access), the PIO (Parallel Input-Output) and the DART (Dual Asynchronous Receiver Transmitter). As the product line developed, low-power, high-speed and CMOS versions of these chips were produced.

In the same manner as the x86 family, but unlike contemporary 8-bit processors, like the Motorola 6800 and Mos Technology 6502, the Z80 and 8080 had a separate control line and address space for I/O instructions. While some Z80-based computers used "Motorola-style" memory mapped input/output devices, usually the I/O space was used to address one of the many Zilog peripheral chips compatible with the Z80. Zilog I/O chips supported the Z80's new mode 2 interrupts (see description above) which simplified interrupt handling for large numbers of peripherals.

'Undocumented' 16 bit I/O-addressing

The Z80 was officially described as supporting 16 bit (64 KB) memory addressing, and 8 bit (256 ports) I/O-addressing. Looking carefully at the hardware reference manual, it can be seen that all I/O instructions actually assert the entire 16-bit address bus. OUT (C),reg and IN reg,(C) places the contents of the entire 16 bit BC register on the address bus;[38] OUT (n),A and IN A,(n) places the contents of the A register on b8-b15 of the address bus and n on b0-b7 of the address bus. A designer could choose to decode the entire 16 bit address bus on I/O operations in order to take advantage of this feature, or use the high half of the address bus to select subfeatures of the I/O device. This feature has also been used to minimise decoding hardware requirements, such as in the Amstrad CPC and ZX81.

Second sources, derivatives etc.

Second sources

NEC's μPD780C Z80 clone.
Sharp's LH0080A Z80 clone
The T34BM1, a Russian Z80 clone.
The Toshiba TMPZ84C015 - a plain Z80 with many peripheral- and other functions on chip.
Hitachi HD64180

Mostek MK3880 and SGS-Thomson Z8400 (now STMicroelectronics) were both second-sources for the Z80. Sharp and NEC developed clones in NMOS, the LH0080 and µPD780C respectively. Toshiba made a CMOS-version, the TMPZ84C00, which is believed (but not verified) to be the same design also used by Zilog for its own CMOS Z84C00. There were also Z80-chips marked GoldStar and LG.

In East Germany, an unlicensed clone of the Z80, known as the U880, was manufactured. It was very popular and was used in Robotron's and VEB Mikroelektronik Mühlhausen's computer systems (e.g. the KC85-series) and also in many self-made computer systems (ex. COMP JU+TER). In Romania another unlicensed clone could be found, named MMN80CPU and produced by Microelectronica, used in home computers like TIM-S, HC, COBRA.

Also, several clones of Z80 were created in the Soviet Union, notable ones being the T34BM1, also called КP1858ВМ1. (This paralleled other Russian chips such as the KR580VM80A, which was a clone of the Intel 8080.) The first marking was used in pre-production series, while the second had to be used for a larger production. Though, due to the collapse of Soviet microelectronics in late 80s, there are much more T34BM1 than КP1858ВМ1.


Compatible with the original Z80
  • Hitachi developed the HD64180, a microcoded and partially dynamic Z80 in CMOS, with on chip peripherals and a simple MMU giving a one MB address space. It was later second sourced by ZiLOG, initially as the Z64180, and then in the form of the slightly modified Z180[39] which has bus protocol and timings better adapted to Z80 peripheral chips. Z180 has been maintained and further developed under ZiLOG's name, the newest versions being based on the fully static S180/L180 core with very low power draw and EMI (noise).
  • Toshiba developed the 84 pin Z84013 / Z84C13 and the 100 pin Z84015 / Z84C15 series of "intelligent peripheral controllers", basically ordinary NMOS and CMOS Z80 cores with large numbers of Z80 peripherals, watch dog timer, power on reset, and wait state generator on chip. These products are today second sourced by ZiLOG.[40]
  • The 32-bit Z80 compatible ZiLOG Z380, introduced 1994, has survived but never gained real momentum; it is used mainly in telecom equipment.
  • Kawasaki developed the binary compatible KL5C8400 which executes instructions about four times faster than the original Z80, [41] is appoximately 1.2 to 1.3 times as clock cycle efficient as the original Z80 and can be clocked at up to 33 MHz., as well as the KL5C80A12 family,[41] which has peripherals as well as a small RAM on chip, is appoximately as clock cycle efficient as the eZ80 and can be clocked at up to 10 MHz.
  • ZiLOG's fully pipelined Z80 compatible eZ80[42] with an 8/16/24-bit word length and a linear 16 MB address space was introduced in 2001. It exists in versions with on chip SRAM and/or flash memory, as well as with integrated peripherals. One variant has on chip MAC (media access controller), and available software include a TCP/IP stack. Contrasting to Z800 and Z280, there are only a few added instructions (primarily LEAs, PEAs, and variable-address 16/24-bit loads), but instructions are instead executed between two and 11 times as clock cycle efficient as on the original Z80. It can be clocked at up to 50 MHz.
  • The Chinese Actions Semiconductor's audio processor family of chips (ATJ2085 and others) contains a Z80-compatible MCU together with a 24-bit dedicated DSP processor.[43] These chips are used in a large number of MP3 and media player products.
  • The Toshiba TLCS 900 series of high volume (mostly OTP) microcontrollers are based on the Z80; they share the same basic BC,DE,HL,IX,IY register structure, and largely the same instructions, but are not binary compatible, while the previous TLCS 90 is compatible.[44]
  • Rabbit Semiconductor's Rabbit 2000/3000/4000 microprocessors/microcontrollers[45] are based on the HD64180/Z180 architecture, although they are not binary compatible.[46]

No longer produced:

  • The ASCII Corporation R800 was a fast 16-bit processor used in certain MSX computers; it was software, but not hardware compatible with the Z80.
  • Zilog's ill-fated NMOS Z800 and CMOS Z280 were quite fast Z80-implementations (before the HD64180 / Z180) with a 16 MB paged MMU address space; they added many orthogonalizations and addressing modes to the Z80 instruction set, but were too complex and mini-computer inspired to be a natural choice for most embedded applications.[47] In contrast, the plain CMOS Z80 has remained popular, alongside the compatible Z180 and eZ80 families.

FPGA and ASIC versions

A commercial, functionally equivalent, CPU core is the Evatronix CZ80CPU,[48] available as synthesizable VHDL or Verilog source code, for high volume ASICs, or as post-synthesis EDIF netlists, for low volume FPGAs from Actel, Altera, Lattice or Xilinx.

Free versions are the T80 and TV80, available as VHDL and Verilog sources under a BSD style license.[49][50][51] The VHDL version, once synthesized, can be clocked up to 35 MHz on a Xilinx Spartan II FPGA. For large production series, it's much cheaper to use a traditional solution (or ASIC) than an FPGA, however.

Software emulation

Software emulation of the Z80 instruction set on modern PCs runs faster than the original Z80 CPU ran and is used for home computer simulators (such as Amstrad CPC, MSX and Sinclair ZX Spectrum) and also for video game emulators such as MAME, which executes 1980s vintage video games. SIMH emulates MITS Altair 8800 computer with Intel 8080, Zilog Z80 or Intel 8086 processors.

Notable uses

In desktop computers

For a comprehensive overview, see the List of home computers using the Z80.

During the late 1970s and early 1980s, the Z80 was used in a great number of fairly anonymous business-oriented machines with the CP/M operating system, a combination that dominated the market at the time.[52][53]

Two well-known examples of Z80+CP/M business computers are the portable Osborne 1 and the Kaypro series. Research Machines manufactured the 380Z and 480Z microcomputers which were networked with a thin Ethernet type LAN and CP/NET in 1981. Other manufacturers of such systems included Televideo, Xerox (820 range) and a number of more obscure firms. Some systems used multi-tasking operating system software to share the one processor between several concurrent users.

Home computers using the Z80 (or equivalent) include the following:

Other 6502 architecture computers on the market at the time, such as the BBC Micro, Apple II[66] and the 6510 based Commodore 64,[67] could make use of the Z80 with an external unit, a plug-in card, or an expansion cartridge. The Microsoft Z-80 SoftCard for the Apple II was a particularly successful add-on card and one of Microsoft's few hardware products of the era.

  • The Z80 was also used in the Norwegian Tiki 100 computers, which were the computers of choice in Norwegian primary schools during the late 1980s.
  • The Acer company, formerly Multitech, introduced the Microprofessor I, in 1981. It was designed as a simple and inexpensive training system for the Z80 microprocessor. Currently, it is still being manufactured and sold by Flite Electronics International Limited in Southampton, England
  • A Z80A Polish clone was also used in the Sinclair ZX Spectrum clones produced by Polish company Elwro.
  • In Romania, several Z80 based computers were manufactured: HC85, HC90, HC91, HC2000 (by the Felix Computers Factory, based in Bucharest), CIP-02, CIP-03 and CIP-04 (by the Electronica Factory, located in Bucharest) and TimS, microTIM and TimS+ (designed by several professors from Timişoara Technical University).

In embedded systems and consumer electronics

Z80 based PABX. The Z80 is to the right of the chip which has a label stuck on.

The Zilog Z80 has long been a popular microprocessor in embedded systems and microcontroller cores,[20] where it remains in widespread use today.[9][56] The following list provides examples of such applications of the Z80, including uses in consumer electronics products.


Consumer electronics

Musical instruments, etc.

See also

Further reading

Articles about Z80 architecture

  • El-Hajj A, Kabalan KY, Mneimneh M, Karablieh F (August 2000). "Microprocessor simulation and program assembling using spreadsheets". Simulation 75 (2): 82–90. doi:10.1119/1.14604.  
  • Nagasawa K, Taki K, Tamemoto H, Lee BY, Tanaka H, Imai S, Kajikawa Y, Azuma D (April 1997). "Design and evaluation for super low power Z80 with pass-transistor logic". Sharp Technical Journal 67: 35–40.  
  • Smith MF, Luff BE (1984). "Automatic Assembler Source Translation From The Z80 To The Mc6809". IEEE Micro (IEEE) 4 (2): 3–9. doi:10.1109/MM.1984.291314.  

Educational uses

  • Mudge TN, Buzzard GD (1983). "Teaching Assembly Language Programming With ZIP, A Z80 Assembly Language Interpreter Program". IEEE Transactions on Education (IEEE) 26 (3): 91–98. doi:10.1109/TE.1983.4321615.  
  • Microprofessor I Z80 System hardware, associated coursework & training manuals.

Scientific applications


  1. ^ Anderson 1994, p. 51
  2. ^ Anderson 1994, p. 57
  3. ^ a b Brock, Gerald W. (2003). The second information revolution. Harvard University Press. ISBN 9780674011786.  
  4. ^ "History of the 8-bit: travelling far in a short time". InfoWorld (InfoWorld Media Group): 58. 29 November 1982. ISSN 0199-6649.  
  5. ^ Mathur. Introduction to Microprocessors. p. 111. ISBN 9780074602225. "The register architecture of the Z80 is more innovative than that of the 8085"  
  6. ^ Ciarcia 1981, pp. 31,32
  7. ^ a b Wai-Kai Chen (2002). The circuits and filters handbook. CRC Press. p. 1943. ISBN 9780849309120. "[...] interrupt processing commences according to the interrupt method stipulated by the IM i, i=0, 1, or 2, instruction. If i=1, for direct method, the PC [...] is loaded with 0038H. If i=0, for vectored method, [...] the interrupting device has the opportunity to place the op-code for one byte [...]. If i=2, for indirect vector method, [...] the interrupting device must then place a byte [...]. The Z80 then uses this byte [...] where one of 128 interrupt vectors can be selected by the byte [...]."  
  8. ^ Adrian, Andre. "Z80, the 8-bit Number Cruncher".  
  9. ^ a b c Balch, Mark (2003-06-18). "Digital Fundamentals". Complete Digital Design: A Comprehensive Guide to Digital Electronics and Computer System Architecture. Professional Engineering. New York, New York: McGraw-Hill Professional. p. 122. ISBN 0-07-140927-0.  
  10. ^ The Seybold report on professional computing. Seybold Publications. 1983. "In the 8-bit world, the two most popular microcomputers are the Z80 and 6502 computer chips."  
  11. ^ Popular Computing. McGraw-Hill. 1983. p. 15.  
  12. ^ Markoff, John (18 October 1982). "Zilog's speedy Z80 soups up 8-bit to 16-bit perfofrmance". InfoWorld (InfoWorld Media Group): 1. ISSN 0199-6649.  
  13. ^ Margins are great, and most chips actually work well at significantly higher (such as 2x) clock frequencies than specified; memory speed has often been the real (physical) limiting factor up until the last 15 years or so, when cheaper and faster available memory chips changed this relation.
  14. ^ Made possible by fully static gate structures.
  15. ^ Electronic design. Hayden. 1988. p. 142. "In addition to supporting the entire Z80 instruction set, the Z180 [...]"  
  16. ^ Ganssle, Jack G. (1992). "The Z80 Lives!". "The designers picked an architecture compatible with the Z80, giving Z80 users a completely software compatible upgrade path. [...] The 64180 processor runs every Z80 instruction exactly as a Z80 does"  
  17. ^ Kilobaud. 1001001. 1977. p. 22.  
  18. ^ Zaks, Rodnay (1982). Programming the Z80 (3rd ed.). SYBEX. p. 62. ISBN 9780895880697.  
  19. ^ According to one of the designers, Masatoshi Shima, the market focus was on high performance printers, high-end cash registers, and intelligent terminals.
  20. ^ a b c Steve Heath. (2003). Embedded systems design. Oxford: Newnes. p. 21. ISBN 9780750655460.  
  21. ^ While R is an 8 bit register, it wraps around at 128 instead of 256. If the programmer stores a value in the register, its high bit will be preserved regardless of what the CPU does to the remaining 7 bits. Incorrect implementation of this behaviour is a common source of problems when running games on emulated Z80-machines
  22. ^ Frank Durda IV. "8080/Z80 Instruction Set".  
  23. ^ Jump (JP) instructions, which load the program counter with a new instruction address, do not themselves access memory. Absolute and relative forms of the jump reflect this by omitting the round brackets from their operands. Register based jump instructions such as "JP (HL)" include round brackets in an apparent deviation from this convention. "Z80 Relocating Macro Assembler User's Guide". p. Page B-2.  
  24. ^ Surprisingly, only quite superficial similarities (such as the word MOV, or the letter X, for extended register) exists between the 8080 and 8086 assembly languages, despite the fact that 8080 programs can be compiled into x86 code (using a special assembler) (Scanlon, Leo J. (1988). 8086/8088/80286 assembly language‎. Brady Books. p. 12. ISBN 9780132469197. "The 8086 is software-compatible with the 8080 at the assembly-language level."  Nelson, Ross P. (1988). The 80386 book: assembly language programmer's guide for the 80386‎. Microsoft Press. p. 2. ISBN 9781556151385. "An Intel translator program could convert 8080 assembler programs into 8086 assembler programs"  )
  25. ^ a b "Z80 CPU Introduction". ZiLOG. 1995. "It has a language of 252 root instructions and with the reserved 4 bytes as prefixes, acceses an additional 308 instructions."  
  26. ^ . p. 65. ISBN 9781420043020. "The 8-bit microprocessors that preceded the 80x86 family (such as the Intel 8080, the Zilog Z80, and the Motorola) did not include multiplication [...]"  
  27. ^ The 10-year-newer microcoded Z180 design could initially afford more "chip area", permitting a slightly more efficient implementation (using a wider ALU, among other things), similar things can be said for the Z800, Z280, and Z380. However, it was not until the fully pipelined eZ80 was launched in 2001 that those instructions finally became approximately as cycle-efficient as it is technically possible to make them, i.e. given the Z80 encodings combined with the capability to do an 8-bit read or write every clock cycle.
  28. ^ Froehlich, Robert A. (1984). The free software catalog and directory. Crown Publishers. p. 133. ISBN 9780517554487. "Undocumented Z80 codes allow 8 bit operations with IX and IY registers."  
  29. ^ a b Bot, Jacco J. T.. "Z80 Undocumented Instructions". Home of the Z80 CPU. "If an opcode works with the registers HL, H or L then if that opcode is preceded by #DD (or #FD) it works on IX, IXH or IXL (or IY, IYH, IYL), with some exceptions. The exeptions are instructions like LD H,IXH and LD L,IYH [...]"  
  30. ^ InfoWorld (InfoWorld Media Group) (Vol. 4, Num. 24): 23. 21 June 1982. ISSN 0199-6649. "After the command summary are examples and two pages of undocumented Z80 operation codes.".  
  31. ^ ZiLOG (2005). Z80 Family CPU User Manual. ZiLOG. p. 11.  
  32. ^ Ciarcia 1981, p. 65
  33. ^ . p. 200. ISBN 9780895880697. "ADD A, n Add accumulator with immediate data n. [...] MEMORY Timing: 2 M cycles; 7 T states"  
  34. ^ Ciarcia 1981, p. 63
  35. ^ Ciarcia 1981, p. 77
  36. ^ Ciarcia 1981, p. 36
  37. ^ Ciarcia 1981, p. 58
  38. ^ Young, Sean (1998). "Z80 Undocumented Features (in software behaviour)". "The I/O instructions use the whole of the address bus, not just the lower 8 bits. So in fact, you can have 65536 I/O ports in a Z80 system (the Spectrum uses this). IN r,(C), OUT (C),r and all the I/O block instructions put the whole of BC on the address bus. IN A,(n) and OUT (n),A put A*256+n on the address bus."  
  39. ^ Ganssle, Jack G. (1992). "The Z80 Lives!". "The 64180 is a Hitachi-supplied Z80 core with numerous on-chip "extras". Zilog's version is the Z180, which is essentially the same part."  
  40. ^ Ganssle, Jack G. (1992). "The Z80 Lives!". "Both Toshiba and Zilog sell the 84013 and 84015, which are Z80 cores with conventional Z80 peripherals integrated on-board."  
  41. ^ a b Electronic Business Asia. Cahners Asia Limited. 1997. p. 5. "Kawasaki's KL5C80A12, KL5C80A16 and KL5C8400 are high speed 8-bit MCUs and CPU. Their CPU code, KC80 is compatible with Zilog's Z80 at binary level. [...] KC80 executes instructions about four times faster than Z80 at the same clock rate [...]"  
  42. ^ "EZ80 ACCLAIM Product Family". ZiLOG.  
  43. ^ "Hardware specs". 2005.  
  44. ^ "Section 6 MOS MPU, MCU, and Peripherals Market Trends". p. 16.  
  45. ^ Axelson, Jan (2003). Embedded ethernet and internet complete. Lakeview research. p. 93. ISBN 9781931448000. "[...] Rabbit Semiconductor's Rabbit 3000 microprocessor, which is a much improved and enhanced derivative of ZiLOG, Inc.'s venerable Z80 microprocessor."  
  46. ^ Hyder, Kamal; Perrin, Bob (2004). Embedded systems design using the Rabbit 3000 microprocessor. Newnes. p. 32. ISBN 9780750678728. "The Rabbit parts are based closely on the Zilog Z180 architecture, although they are not binary compatible with the Zilog parts."  
  47. ^ Minicomputer features such as, user and system modes, multiprocessor support, on chip MMU, on chip instruction and data cache, etc. was seen rather as more complexity than as functionality and support for the (usually electronics-oriented) embedded systems designer, it also made it very hard to predict instruction execution times.
  48. ^ "CZ80CPU - 8-bit Microprocessor Core". Cast.  
  49. ^ "T80 cpu :: Overview".  
  50. ^ "TV80 :: Overview".  
  51. ^ "TV 80 Home Page".  
  52. ^ Holtz, Herman (1985). Computer work stations. Chapman and Hall. p. 223. ISBN 9780412004919. "[...] and CP/M continued to dominate the 8-bit world of microcomputers."  
  53. ^ Dvorak, John C. (10 May 1982). "After CP/M, object oriented operating systems may lead the field". InfoWorld (InfoWorld Media Group) (Vol. 4, Num. 18): 20. ISSN 0199-6649. "The idea of a generic operating system is still in its infancy. In many ways it begins with CP/M and the mishmash of early 8080 and Z80 computers.".  
  54. ^ Technical Specification, CPC464 Service Manual, p. 2., Amstrad Consumer Electronics Plc.
  55. ^ Ball, A.; Stirling, A.. "Old computers: Amstrad PCW 8256 and 8512". Retrieved 2009-05-01.  
  56. ^ a b Ian R. Sinclair. (2000). Practical electronics handbook. Oxford, Angleterre: Newnes. p. 204. ISBN 9780750645850.  
  57. ^ British firm unveils micros at Consumer Electronics Show. 6 February 1984. p. 62. ISSN 0199-6649. "The Enterprise's Z80 runs at a speed of 4 MHz, [...]".  
  58. ^ . p. 40. ISBN 9788468992808. "Micro Z80 a 3.25 MHz [...], el Jupiter Ace [...]"  
  59. ^ . p. XV. ISBN 9781590598313. "Then I met the ABC80, a Swedish computer from Luxor. It had the same Z80 processor [...]"  
  60. ^ . p. 41. ISBN 9788468992808. "[...] el Sam Coupé tenía el z80 de Zilog [...]"  
  61. ^ Dvorak, John C. (7-14 January 1985). "MSX: The pong of the 1980s". InfoWorld (InfoWorld Media Group) (Vol. 7, Num. 1-2): 88. ISSN 0199-6649.  
  62. ^ "Spectravideo SV-328". 2008. Retrieved 2009-07-17.  
  63. ^ Laing, Gordon (2004). Digital Retro. The Ilex Press. ISBN 9781904705390.  
  64. ^ InfoWorld (Vol. 6, Num. 17): 66. 23 April 1984. ISSN 0199-6649.  
  65. ^ Byte. McGraw-Hill. 1986. p. 274. "C-128 CP/M uses both the Z80 and 8502 processors. The Z80 executes most of the CP/M BIOS functions."  
  66. ^ Petersen, Marty (6 February 1984). "Review: Premium Softcard IIe". InfoWorld (InfoWorld Media Group) (Vol. 6, Num. 6): 64. "Several manufacturers, however, make Z80 coprocessor boards that plug into the Apple II.".  
  67. ^ Popular Computing. McGraw-Hill. 1986. p. 22. "The Commodore 64 CP/M package contains a plug-in cartridge with a Z80 microprocessor and the CP/M operating system on a disk."  
  68. ^ A. Meystel. (1991). Autonomous mobile robots : vehicles with cognitive control. Teaneck, N.J.: World Scientific. p. 44. ISBN 9789971500894.  
  69. ^ American Society of Cinematographers (1983). American cinematographer. ASC Holding. p. 18.  
  70. ^ Bruce A. Artwick. (1980). Microcomputer interfacing.. Englewood Cliffs, N.J.: Prentice-Hall: Prentice-Hall. p. 25. ISBN 9780135809020.  
  71. ^ Anderson, Nate. "Source code requests force breathalyzer maker to sober up". Ars Technica. "The Intoxilyzer 5000EN, a breathalyzer [...], runs on a pair of Z80 processors"  
  72. ^ Campbell, Robert (2001). "TI-82/83/85/86 Mathematics Use". UMBC.  
  73. ^ Miesenberger, Klaus (2008). Computers Helping People with Special Needs. Berlin: Springer. p. 556. ISBN 9783540705390.  
  74. ^ "Game Board Schematic" (pdf). Midway Pac-Man Parts and Operating Manual. Chicago, Illinois: Midway Games. December 1980. pp. 32, 35. Retrieved 2009-07-20.  
  75. ^ Nitsche, Michael (2009-03-31). "Games and Rules". Video Game Spaces: Image, Play, and Structure in 3D Worlds. Cambridge, Massachusetts: MIT Press. p. 26. ISBN 0-262-14101-9. "[...] they would not realize the fundamental logical difference between a version of Pac-Man (Iwatani 1980) running on the original Z80 [...]"  
  76. ^ "Game Logic Schematic" (pdf). Midway Galaxian Parts and Operating Manual. Chicago, Illinois: Midway Games. February 1980. pp. 22, 24. Retrieved 2009-07-20.  
  77. ^ "Schematics and Wiring Diagrams" (pdf). Midway Galega Parts and Operating Manual. Chicago, Illinois: Midway Games. October 1981. pp. 7–7 – 7-9, 7-14. Retrieved 2009-07-20.  
  78. ^ InfoWorld (Vol. 4, No. 50): 33. 20 December 1982. ISSN 0199-6649. "The ColecoVision uses the Z80 microprocessor".  
  79. ^ Daniel Sanchez-Crespo Dalmau. (2004). Core techniques and algorithms in game programming. Indianapolis, Ind.: New Riders. p. 14. ISBN 9780131020092. "Internally, both the NES and Master System were equipped with 8-bit processors (a 6502 and a Zilog Z80, respectively)"  
  80. ^ Joe Grand, Albert Yarusso. (2004). Game console hacking : Xbox, PlayStation, Nintendo, Game Boy, Atari, & Sega. Rockland, Mass.: Syngress. p. 182. ISBN 9781931836319. "This first Game Boy operated on four AA batteries and was equipped with a Zilog Z80 microprocessor — the same processor used on many electronic devices in the 1980s. In fact, all the Game Boy models up to and including the Game Boy Color featured a Z80 CPU"  
  81. ^ Reid, Gordon (1999). "The Prophet 5 and Prophet 10". "Although the Prophet 5s and Prophet 10s incorporated Z80 microprocessors, [...]"  
  82. ^ "About MemoryMoog". Moog MemoryMoog User Group. "CPU is Z80 + Z80CTC"  


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