Talk:Contended I/O

From Sinclair Wiki
Revision as of 13:05, 30 May 2015 by Szaszg (talk | contribs) (ULA really makes Z80 to go WAIT state instead of HALT it)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to navigation Jump to search

IMHO the "... the ULA halts the processor" is not the best phrase, because there is a HALT instruction in Z80 assembly, which really halt the CPU and the processor is halted while an interrupt arrived. Hmm... o.k. not exactly, because Z80 do NOPs to refresh memory.

This situation the ULA really pulls the "/WAIT" pin of CPU, and Z80 adds "empty" clock cycles while /WAIT is low. BTW: while Z80 waits, does not refresh the memory, so a long wait cycle can "erase" the DRAM...

Retrieved from ‘https://sinclair.wiki.zxnet.co.uk/w/index.php?title=Talk:Contended_I/O&oldid=1361’