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82C554
Input ControlSlgnalDcllnltlon
SfE (Strole Input). A "low" on this input loads
dataintothe inputlatch.
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IBF(lnputBuflcr FullF/F)
ffi^
lfe
A "high" on this outputindicatesthat the data has
beenloadedintothe inputlatch;in essence,an acknowledgement.
IBF is set by STBingl beinglow
and is resetby the risingedgeof th€ RD input.
lfti^
tro
ll{TR (lntenupt Requeat)
rmt r |r0l?al
A "high" on this outputcan be us€dto intenuptthe
CPU when an input deviceis requestingservice.
INTRis s€t by the STEis a "ono", IBFis a "one"
and INTEis e "on€". lt is resetby thefallingedgeof
HD. ttris procedureallowsan input deviceto requestservicefrom the CPUby simplystrobingits
dataintothe port.
INTEA
controlledby bit set/res€tof Pc4.
INTEB
controlledby bit set/resetot Pc2.
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Flgure8. ilODE I Input
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xt,?tto'lr|,xar/rt
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2312*-11
Flgure9. ilODE 1 (Strobcdlnput)
3-134