Zilog eZ80
Encyclopedia
The Zilog
eZ80 is an 8-bit
microprocessor
which is essentially an updated version of the company's earlier Z80
8-bit microprocessor.
The eZ80 (like the Z380) is binary compatible with the Z80 and Z180, but almost four times as fast as the original Z80 chip at the same clock frequency. Available at up to 50 MHz (2004), the performance is comparable to a Z80 clocked at 200 MHz if fast memory is used (i.e. no wait states for opcode
fetches, for data, or for I/O) or even higher in some applications (a 16-bit addition is 11 times as fast as in the original). The eZ80 also supports direct continuous addressing of 16 MB
of memory without a memory management unit
, by extending most registers (HL, BC, DE, IX, IY, SP, and PC) from 16 to 24 bits.
The processor has a 24-bit ALU (Arithmetic Logic Unit
) and overlapped processing of several instructions (a so called pipeline) which are the two primary reasons for its speed. Unlike the older Z280 and Z380 it does not have (or need) a cache memory. Instead, it is intended to work with fast SRAM directly as main memory (as this has become much cheaper). Nor does it have the multiplexed bus of the Z280, making it as easy to work with (interface to) as the original Z80 and Z180, and equally predictable when it comes to exact execution times.
The chip has a memory interface that is similar to the original Z80, including the bus request/acknowledge pins, and adds four integrated chip selects. Versions are available with on-chip flash memory and on-chip zero wait-state SRAM (up to 256 KB
Flash memory and 16 KB SRAM) but there are also external buses on all models. The eZ80 supports a free TCP/IP stack and operating system based on the Xinu
operating system, as well as a real-time kernel.
Zilog
Zilog, Inc., previously known as ZiLOG , is a manufacturer of 8-bit and 24-bit microcontrollers, and is most famous for its Intel 8080-compatible Z80 series.-History:...
eZ80 is an 8-bit
8-bit
The first widely adopted 8-bit microprocessor was the Intel 8080, being used in many hobbyist computers of the late 1970s and early 1980s, often running the CP/M operating system. The Zilog Z80 and the Motorola 6800 were also used in similar computers...
microprocessor
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
which is essentially an updated version of the company's earlier Z80
Zilog Z80
The Zilog Z80 is an 8-bit microprocessor designed by Zilog and sold from July 1976 onwards. It was widely used both in desktop and embedded computer designs as well as for military purposes...
8-bit microprocessor.
The eZ80 (like the Z380) is binary compatible with the Z80 and Z180, but almost four times as fast as the original Z80 chip at the same clock frequency. Available at up to 50 MHz (2004), the performance is comparable to a Z80 clocked at 200 MHz if fast memory is used (i.e. no wait states for opcode
Opcode
In computer science engineering, an opcode is the portion of a machine language instruction that specifies the operation to be performed. Their specification and format are laid out in the instruction set architecture of the processor in question...
fetches, for data, or for I/O) or even higher in some applications (a 16-bit addition is 11 times as fast as in the original). The eZ80 also supports direct continuous addressing of 16 MB
Megabyte
The megabyte is a multiple of the unit byte for digital information storage or transmission with two different values depending on context: bytes generally for computer memory; and one million bytes generally for computer storage. The IEEE Standards Board has decided that "Mega will mean 1 000...
of memory without a memory management unit
Memory management unit
A memory management unit , sometimes called paged memory management unit , is a computer hardware component responsible for handling accesses to memory requested by the CPU...
, by extending most registers (HL, BC, DE, IX, IY, SP, and PC) from 16 to 24 bits.
The processor has a 24-bit ALU (Arithmetic Logic Unit
Arithmetic logic unit
In computing, an arithmetic logic unit is a digital circuit that performs arithmetic and logical operations.The ALU is a fundamental building block of the central processing unit of a computer, and even the simplest microprocessors contain one for purposes such as maintaining timers...
) and overlapped processing of several instructions (a so called pipeline) which are the two primary reasons for its speed. Unlike the older Z280 and Z380 it does not have (or need) a cache memory. Instead, it is intended to work with fast SRAM directly as main memory (as this has become much cheaper). Nor does it have the multiplexed bus of the Z280, making it as easy to work with (interface to) as the original Z80 and Z180, and equally predictable when it comes to exact execution times.
The chip has a memory interface that is similar to the original Z80, including the bus request/acknowledge pins, and adds four integrated chip selects. Versions are available with on-chip flash memory and on-chip zero wait-state SRAM (up to 256 KB
Kilobyte
The kilobyte is a multiple of the unit byte for digital information. Although the prefix kilo- means 1000, the term kilobyte and symbol KB have historically been used to refer to either 1024 bytes or 1000 bytes, dependent upon context, in the fields of computer science and information...
Flash memory and 16 KB SRAM) but there are also external buses on all models. The eZ80 supports a free TCP/IP stack and operating system based on the Xinu
Xinu
Xinu is a Unix-like operating system originally developed by Douglas Comer for instructional purposes at Purdue University in the 1980s. The name is both recursive, and is "Unix" spelled backwards...
operating system, as well as a real-time kernel.
Variants
- eZ80Acclaim! is a family of eZ80 single chip computers labeled as "application-specific standard products" (ASSP) that feature up to 128 KB of Flash memory, up to 8 KB of SRAM, and can operate at speeds of up to 20 MHz. Like other eZ80 variants, it has an external address and data bus and can thus be used as a general purpose microprocessor as well.
- eZ80AcclaimPlus! is a family of connectivity ASSPs that feature up to 256 KB of Flash memory, 16 KB of SRAM, can operate at speeds of up to 50 MHz. It adds an integrated 10/100BaseT EthernetEthernetEthernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
MACMedia Access ControlThe media access control data communication protocol sub-layer, also known as the medium access control, is a sublayer of the data link layer specified in the seven-layer OSI model , and in the four-layer TCP/IP model...
, TCP/IP stack over the eZ80Acclaim! line. Like other eZ80 variants, it has an external address and data bus and can thus be used as a general purpose microprocessor as well.