Bugs

Zilog NMOS ld a,{i|r}

Due to a bug, Z80 NMOS models from Zilog reset PF when an INT is accepted during the execution of the ld a,{i|r} instructions.

References

• Zilog (1989-01). "Z80 Family Data Book", pp. 412-413.
• Roshchin, Ivan (1998). "Undocumented Feature of the Z80 Processor".

Zilog CMOS out (c),0

The out (c),0 instruction behaves as out (c),255 on Z80 CMOS models from Zilog.

This was first discovered by Simon Cooke, who reported it on Usenet in 1996. Later, in 2004, Colin Piggot rediscovered it with his SAM Coupé when running a demo for SCPDU 6, coincidentally written by Simon Cooke. In 2008, this was once again rediscovered by the MSX community.

References

• https://sinclair.wiki.zxnet.co.uk/wiki/Z80

Special RESET during the HALT state

See Tony Brewer's article.