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Z80: Difference between revisions
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Add information about Z80 variants and clones
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The instruction set of the Z80 in an extension of that of the Intel 8080. An entirely different set of assembly mnemonics is used. 8080 compatibility allowed the Z80 to be used in many CP/M systems, and this compatibility allowed CP/M to run on the ZX Spectrum +3, and a CP/M compatible system, Pro-DOS, to run on the SAM Coupé. | The instruction set of the Z80 in an extension of that of the Intel 8080. An entirely different set of assembly mnemonics is used. 8080 compatibility allowed the Z80 to be used in many CP/M systems, and this compatibility allowed CP/M to run on the ZX Spectrum +3, and a CP/M compatible system, Pro-DOS, to run on the SAM Coupé. | ||
Zilog have released | [[Zilog]] have released a number of variants of the Z80, and it has been second-sourced by many manufacturers, such as Mostek. In addition, there are numerous processors such as the R800 and T80 that are largely compatible with the Z80's instruction set. | ||
[[NEC]] produced an unlicensed clone of the Z80 ([http://archive.computerhistory.org/resources/access/text/Oral_History/102658073.05.01.acc.pdf Computer History Museum: Z80 oral history] page 13) through reverse engineering. It is this clone, the NEC µPD780 that is found in the majority of Spectrums, labelled as a "D780C -1". | |||
The [[Wikipedia:ru:Т34ВМ1 и Т34ВГ1|КР1858ВМ1]] (link to Russian language Wikipedia) was produced in the Soviet Union, and in East Germany, the [[Wikipedia:de:U880|U880]] (link to German language Wikipedia) was manufactured. These differ from the Zilog Z80 in their setting of the carry flag after an OUTI operation, but are otherwise (almost?) identical. | |||
== Contended memory == | == Contended memory == | ||
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=== BIT n,(HL) === | === BIT n,(HL) === | ||
Upon executing BIT n,(HL) instructions, bits 3 and 5 of the F register are copied from an internally buffered register pair now commonly referred to as MEMPTR, as described in [http://zx.pk.ru/attachment.php?attachmentid=2989 memptr_eng.txt]. | Upon executing BIT n,(HL) instructions, bits 3 and 5 of the F register are copied from an internally buffered register pair now commonly referred to as MEMPTR or WZ, as described in [http://zx.pk.ru/attachment.php?attachmentid=2989 memptr_eng.txt]. | ||
Woody has confirmed that bits 3 and 5 of the flags are copied on all BIT instructions on both a Zilog Z80 and an NEC clone (stated on the link above as being "unverified"). | Woody has confirmed that bits 3 and 5 of the flags are copied on all BIT instructions on both a Zilog Z80 and an NEC clone (stated on the link above as being "unverified"). | ||