I've looked at the Z80 pins such as MREQ, IORQ, RD and WR and these make sense to me.
http://bitsavers.trailing-edge.com/components/intel/MCS80/98-153B_Intel_8080_Microcomputer_Systems_Users_Manual_197509.pdf
I'm now looking at 8080's equivalent and they are MEMR, INP, OUT, and /WO and these...