ZiLOG Z80 Handbook page 15

The 78 instructions of the 8080 are provided in the Z-80, but the
total number of instructions comes to 158. Many of these are logical
extensions of 8080 instructions, but many are extremely powerful
and a complete departure from the 8080. Fig. 1-2 shows the relative
differences between the 8008, 8080, and Z-80.
All Input/Output and interrupt capability of the 8080 is retained
in the Z-80. I/O is expanded, however, to operate from any CPU
register and to operate in "block" fashion, that is, to facilitate transfer
of many bytes at a time over a programmed (non-DMA) I/O chan-
nel. Interrupts include the standard external interrupt capability of
the 8080, but supplement this with a separate "nonmaskable" inter-
rupt similar to the Motorola MC6800 and MOS Technology MCS
6502. Other interrupt capability allows for interrupt vectoring any
where in memory, rather than just to eight locations in page 0, and
for up to 128 levels of interrupts, rather than eight.
The Z-80 Microcomputer Handbook is divided into three sections.
Section I covers the hardware aspects of the Z-80. Architecture, in-
terface signals and timing, addressing modes, instruction set, flags,
interrupt sequences, interface of memory and I/O devices, and DMA
operation are discussed. When applicable, differences between the
8080 and Z-80 are discussed. Section II discusses Z-80 software,
grouped in similar manner to Zilog Z-80 documentation. Section II
also provides programming examples of Z-80 code. Many times, a
short section of a program will greatly clarify the somewhat pedantic
descriptions of individual instructions. Section III discusses five
microcomputer manufacturers that have built microcomputers
around the Z-80 microprocessor chip. Appendix A provides complete
electrical specifications for the Z-80. Appendix B cross-references
8080 instructions to the Z-80 instruction set and Appendix C provides
a short description of each Z-80 instruction. Appendix D reviews
binary and hexadecimal representation while Appendix E lists
ASCII character codes. The last appendix, Appendix F, lists Z-80
Microcomputer manufacturers.
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