The Zilog Z800 was a 16-bitmicroprocessor designed by Zilog to be released in 1985. It was instruction compatible with their existing Z80, and differed primarily in having larger registers, being able to address more memory, and running at higher speeds. However Zilog essentially ignored the Z800 in favour of their 32-bit Z8000 and it appears the Z800 never entered production.
The main difference compared to the Z80 was the expansion of the register set to 16-bits, which could be used as 8-bit registers when running "classic" Z80 code. True 16-bit operations were added, but it seems it was expected that most instructions would remain 8-bit, and there was no special mode needed to mix the two.
The address bus was likewise expanded to address more memory, internally supporing addresses of up to 24-bits. The chip was offered with either a 19-bit external bus for 512kB RAM, or a full 24-bit bus for 16MB RAM, the only advantage to the smaller bus was a smaller 40-pin package. Like the Z80 before it, the Z800 retained the internal DRAM controller and clock, but added 256 bytes of RAM that could be used either as "scratchpad" RAM, or a cache. When used in cache mode the programmer could configure it as a data or instruction cache, or both, and the internal memory controller then used it to reduce access to (slower) external memory.
Another change was the addition of an optional 16-bit data bus, which doubled the rate at which it could access memory if set up properly. Combined with the two address bus sizes this meant that the chip was offered in a total of four versions:
part #
# of pins
data bus
address bus
Z8108
40
8-bit
19-bit (512kB)
Z8116
40
16-bit
19-bit (512kB)
Z8208
64
8-bit
24-bit (16MB)
Z8216
64
16-bit
24-bit (16MB)
The Z800 was, in most ways, a "super Z80" that would run existing programs at considerably higher speeds. However this same compatibility appears to have doomed it, as the existing Z80 was "good enough" for those still using it in the mid-80's, and those needing more power could easily use one of the existing 32-bit designs coming on the market.
ZiLOG, often seen as Zilog, is a manufacturer of 8-bit CPUs, and are most famous for their Intel 8080-compatible Z80 series.
Zilog was incorporated in California in 1974 by Federico Faggin, who left Intel after working on the 8080, and the Z80 shared many features with it.
Later Zilog introduced 16-bit and 32-bit processors, but these were not particularly successful, and the company refocussed on the microcontroller market, producing both basic CPUs and application-specific standard products (ASSPs) built around a CPU.
ZiLOG, often seen as Zilog, is a manufacturer of 8-bit CPUs, and is most famous for its Intel 8080-compatible Z80 series.
Zilog was incorporated in California in 1974 by Federico Faggin, who left Intel after working on the 8080, and the Z80 was a vast improvement over it (it was faster, etc.).
After the Z80Zilog introduced 16-bit and 32-bit processors, but these were not particularly successful, and the company refocused on the microcontroller market, producing both basic CPUs and application-specific integrated circuits/standard products (ASICs/ASSPs) built around a CPU core.
Feeds |
Contact