Sharp PC-1500 - Page 28

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2-3-6. WAIT function
(interfacing with the
slow access time memory)
Because the CPU access time is very fast, the CPU must be held wi th th e wait sig na l in
order to acc
ess a slow access ti me memory.
Bas ically, the wa ii signal is cr ea ied by ihe externally provided counter, but t he 1/ 0 port
co nt ro ll er with th e programmable wa it tim e control feature (LH85 I I) is u se d for this
purpose. For more details
of this functio n. refer to the section discussing t he l/ 0 port
co
nt roller.
Shown in t
he nex t page is the connection of th e CPU with the l/ 0 port controller.
OS >OMEO
R/ W
M EO
CP U
1/0 fl () rl DM El
MEI
cont ro lle- 1
oo-o
WAI T
WO WI
MEO
wa1 1
cond iti on
ME1
wait
C()nd ih o
,\IJ()- A01 5
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