September 24, 1998

EDN's 25th Annual Microprocessor/Microcontroller Directory

Zilog Z80/80180/80380
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The Z80, 180, and 380 processor families represent three generations of upward-compatible µPs. The Z80 includes 150 instructions, many of which have numerous variants for operand location and addressing modes. The 180 includes 10 additional instructions, and the 380 adds 65 more.

The Z80 and 180 include two banks of registers; each bank comprises an 8-bit accumulator and six 8-bit registers that you can also use as three 16-bit registers. The Z80 and 180 also include two 16-bit index registers and a 16-bit stack pointer and program counter. The 380 quadruples the register set of the Z80 and 180, making eight banks of registers. All registers on the 380 are 32 bits wide.

All Z80, 180, and 380 processors include separate memory- and I/O-address spaces. The Z80 memory-address space is 65 kbytes, and the I/O space accesses as much as 256 bytes. The 180 uses a memory-management unit (MMU) to expand the physical memory-address space to 1 Mbyte and maintains 16-bit-wide logical addresses for Z80 compatibility. The 180 also includes instructions that expand I/O addressing to 16 bits. The 380 has a native mode for Z80-compatible memory addressing and an extended mode that provides 32-bit linear addressing, eliminating the need for the MMU. (Some device versions do not pin out all the address bits.)

Power management: Most members of the Z8018x and Z8038x families include power-management facilities. Sleep mode keeps the main oscillator running to permit quick restart but blocks clocking to the processor and most peripherals to reduce power consumption. Standby mode saves even more power by stopping the oscillator but lengthens the restart time.

Special instructions: Instructions allow you to perform exchanges between registers and between registers and memory. Register-bank-selection instructions allow fast context switching. The architectures support decimal arithmetic via decimal-adjust and rotate-digit-left and -right instructions. The Z80180 adds an 8X8-bit multiply; the Z80380 includes 16X16-bit multiply and divide as well as 32-bit add, subtract, increment, decrement, load, and store. Block-transfer and -search instructions support automatic address incrementing and decrementing. The 380 instruction set includes mode settings; instruction prefixes for identifying 16- or 32-bit data; and new instructions that control whether load, store, and arithmetic instructions operate on 16- or 32-bit data.

Special on-chip peripherals: Z18x devices beyond the Z80180 include memory-chip select, wait-state generation, and general-purpose I/O ports, various mixtures of one or two multiprotocol serial channels, a 16450/16550 "mimic" interface for applications such as PC-internal modems, a bidirectional parallel port, on-chip ROM, and a watchdog timer. The basic Z80380 includes only memory-chip select and wait-state generation, whereas the Z80382 includes four general-purpose I/O ports, two UARTs, two timers, mimic, and watchdog timer from the 180 family, plus eight advanced DMA channels, three high-speed data-link-control channels, a PCMCIA interface, and a plug-and-play ISA interface.

Development tools: Except for one low-cost Z80180 emulator, Zilog relies on third parties for emulation support for the Z80, Z8018x, and Z8038x devices. Emulator support is available from Avocet System (www.2500ad.com), Orion Instruments (www.yokogawa.com), iSystem (www.isystem.com), and Softaid (www.softaid.com). Software support is available from Avocet Systems, IAR Systems (www.iar.com), and Softools Inc (www.softools.com). Zilog supplies several evaluation boards and a low-cost emulator. Unlike with the Z180, development support for the Z380 is minimal; Zilog provides an assembler, an evaluation board, and a Production Languages Corp (www.plcorp.com) C compiler with an optimizer program to improve performance and code size. Microtec (www.microtec.com) offers a Z80380 C compiler.

Second sources: Seven licensed vendors act as second sources for the Z80. Hitachi acts as a second source for the 180. There are no second sources for the 380.

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