All
and more about Sharp
PC
-1
500
at http:/lwww.PC-1500.info
2-2-4. CPU pin description
U'
)
..:::J"('f')('\1.-.0
u
oooooo8
g~~8~8o~~o8
Z<~<<~<<><~<<<<<<<<
R/ W
57
56
55
54
53
52
51
50
49
48
47
46 45 44
43 42
41
40
39
~ ~
07
P4>
59
37
D6
PV
60
36
05
PU
61
35
D4
4>0S
62
34
03
XLO
63
33
02
XU
64
32
01
WAIT
65
31
00
IN7
66
L
H580
1
30
MEO
I
N6
67
29
ME
l
I
N5
68
(T
OP
VIEW)
28
OD
I
N4
69
27
HO
IN3
70
26
Hl
I
N2
71
25
H2
INl
72
24
H3
I
NO
73
23
H4
NC 74
22
H5
NC
75
21
H6
NC
76
20
H7
1 2 3 4 5 6
7 8 9
10
II
12 13 14
15
16
17
18 19
.....
UJ
lfJ
o
_
e>
ou..~ue>
!:Q
-
w
u~~~
~
~c
u~~oc~~-
1
~c~
~ z
mm>mom>>>>>>Z~xxo
Q)
XLO,
XL1
These
arc
external crystal connection pins.
XLO
is the input pin
and
XLI
is the
output
pin. Clock frequency is divided by two inside the CPU. When t
he
2.6M
Hz
crystal
is
co
nnected, the C
PU
opera
tes ·
under
I .3M Hz
of
internal machine cycle.
(j)
ADO ~
AD
1
5
Address
bu
s.
Outputs
from these pins
arc
3-statc (three output states
of
high, low and
high impedance) and
go
high impedance with
BRQ
(Bus ReQuest). Basica
ll
y,
64K
bytes
of
memory
area
is s
uppo
rted for direct
acc
essing,
but
it is
made
possible to access
e
ve
n 128K
area
of memory
area
when MEO
and
M
El
arc
used.
Q)
0
0
~
0
7
Bidirectional
da
ta
bu
s which is used to write
or
da
ta to/ from
the
external m
emo
r
y.
©
MEO
,
ME
1
Memory
enable signals.
As
mem
ory
area
of
64K bytes is accessed by M EOa nd
ano
th
er
64K bytes by
ME
I, it permits direct access
of
memor
y
area
of
1
28
K bytes in total.
Si
nc
e
MEO
is used for instructi
on
fetch
and
sta
ck
ope
ra
ti
on, accessing by m
eans
o'f the
program counter
P
and
stack pointer S is limited to a maximum of 64K bytes.
As
for
data
acce
ss
ing,
both
memory
area
s covered by M
EO
and ME I
ca
n be
con
trolled
by a
CPU in
st
ru
ctio
n.
9
Do
not sell this PDF
!!
!
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