| Zilog Z80 An 8-bit . It was released in July 1976 with a 2.5 MHz . The Z80 was a much improved (as was the ). It also used 8-bit data and 16-bit addressing, and could execute all of the s as well as 80 new ones, instructions that included 1, 4, 8 and 16-bit operations and even block move and block I/O instructions. The was doubled, with two banks of registers (including A and F) that could be switched between. This allowed fast or es. It features 3 types of interrupt mode. The Z80 also added two s (IX and IY) and relocatable s (via the 8-bit IV register). Like many processors (including the ), the Z80 featured many undocumented op codes. Chip area near the edge was used for added instructions, but fabrication made the failure of these high. Instructions that often failed were just not documented, increasing chip yield. Later fabrication made these more reliable. The thing that really made the Z80 popular was the memory interface - the CPU generated it's own signals, which meant easier design and lower system cost. That and its compatibility and , the first standard , made it the first choice of many systems. In addition to the original Z80 (2.5 MHz) there are the (4 MHz), (6MHz) and (8 MHz) versions. The popular processor family adds peripherals and an to the Z80. The was an enhanced version with an and many new s. (1996-06-12) |
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