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Add ''LD A,I and LD A,R in NMOS Z80s'', ''Test programs'', ''See also'' and ''External links'' sections
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(Add ''LD A,I and LD A,R in NMOS Z80s'', ''Test programs'', ''See also'' and ''External links'' sections) |
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In 2008, this was once again [http://www.msx.org/forum/development/msx-development/bug-z80-emulation-or-tr-hw rediscovered by the MSX community]. | In 2008, this was once again [http://www.msx.org/forum/development/msx-development/bug-z80-emulation-or-tr-hw rediscovered by the MSX community]. | ||
== LD A,I and LD A,R in NMOS Z80s == | |||
The NMOS Z80s suffer a problem whereby LD A,I and LD A,R record the state of IFF2 after it has been reset if an interrupt is delivered during that instruction. This behaviour, along with workarounds for this for use in interrupt handlers are documented in the [http://z80.info/zip/ZilogProductSpecsDatabook129-143.pdf Z80 Family Questions and Answers] section of the Zilog Product Specifications Databook. | |||
== Bits 3 and 5 of the F Register == | == Bits 3 and 5 of the F Register == | ||
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|/BUSACK || Bus (DMA) acknowledgement | |/BUSACK || Bus (DMA) acknowledgement | ||
|} | |} | ||
== Test programs == | |||
A basic Flags test program for emulators is available [http://homepage.ntlworld.com/mark.woodmass/z80tests.tap here]. Note that the program makes heavy use of ROM data during the tests and so should only be used with an unpatched copy of the original 48K ROM to obtain correct results. | |||
Patrik Rak has written a [http://zxds.raxoft.cz/taps/misc/z80test.zip Z80 instruction tester], as [http://www.worldofspectrum.org/forums/showthread.php?t=41834 announced here]. | |||
== Replacements == | == Replacements == | ||
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{{CC-BY-SA-techwiki|Z80|Z80}} | {{CC-BY-SA-techwiki|Z80|Z80}} | ||
== See also == | |||
* [X80], a proposed floating point unit following the Spectrum calculator stack instruction set. | |||
== External links == | |||
* Thomas Scherrer's [http://z80.info/ z80.info]: official Zilog manuals and the like | |||
* Sean Young's [http://www.myquest.nl/z80undocumented/ ''The Undocumented Z80 Documented'']: undocumented features | |||
* [http://zx.pk.ru/attachment.php?attachmentid=2989 memptr_eng.txt MEMPTR]: the undocumented flags after BIT n,(HL) | |||