ZiLOG Z80

31
FaultFinding
Checkall links and jumpers,checkno chipshave bent legs and thus not making
contact withtheir socket,carefullyinspectall soldering, check all thechips are
insertedthe right wayround, checkall the componentsare in theright place.
With thePIO modulepluggedin to theRC2014 backplane withno otherboards
fitted.Powerthe backplaneand performthe followingchecks witha volt meter:
 Check the supply voltage onthe PIOmodule,between, say, U1pin 10and U1
pin 20.This shouldbe 4.5 to5.5 volts, preferably 4.75to 5.25 volts.
 Check the interruptenable input (IEI) onconnector P4 isbeing pulledup to at
least 4.5 volts.

Check
each
address
switch
input
(Q2
to
Q7)
on
U1
is
being
pulled
up
to
at
least
4.5 voltswhenthe appropriateswitch (SW1) isOff (open) anddropsto less
than 0.4 voltswhen the appropriateswitch (SW1) isOn (closed).