A
ll
and more about Sharp PC-1500
at
http://www.PC-1500.info
2-4.
Pin
description
IH
XLO,
XL1
Crystal
oscillator
ex
t
erna
l
con
n
ection
p
in
s
(XLO
:
Jn,
XL!
:
Ou
t:)
(2)
ADO
-
AD15
16 bits address bus
(ADO
: least si
gn
ificant address bil, ADI 5: most significant address bit).
Turns high impedance by the BRQ
si
gnal
.
131
D0-07
Bidirectional data bus used
to
write and read data to/from the external memory
(DO:
least
significant
bit,
07:
most significant bit).
(4
) M
EO,
MEl
Memory enable signals
that
the
MPU
uses for direct acces
si
ng:
to
an external memory
of
which
the maximum capacity
is
128
KB
(64KB x
2)
.
(5)1
R/W
Read/write
signal
lhat tlie
MPU
use
to
perform reading operation when
R/W=
I and
writ~
operation when
R/W=O
.
,,.
0 s
ADI
x x
x
L_/
MEO
I
~
MEI
'
'
DI
IN
OUT
Data
read
Data
w(ite
cycle
eye;
le
(6)
RES
ET
A high input
of
this
sign
al causes the
MPU
to
return
to
its initial state.
(7) BRO
Bus
request. A high state
of
this signal causes the
MPU
to
respond with the hi
gh
state
of
the
BAK
signal
upon
comp
le
tion
of
present
command
execution.
(8)
BAK
6
Bus acknowledge appears
in
response with a high
BRQ
indicating that address bus, data bus,
R/W,
ME
O,
and MEI are
in
higl1
impedance.
Do
not
sale this PDF
!!!
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