Sharp PC-7200 Service Manual page 55

OSC1_
OSC2_
V D D -
V S S -
CE
OS
R/W
AS
ADO- AD7
W
Figure 1. Block diagram
Clock
Output
Time Base
~
t..
L.
Input/Ose
-4 -32
-32
+32
+32
rj
j
,
I.,
~
Periodic Interrupt/Square Wave Rate
Selection
(l·of-,5 Selector)
'"
L
D,vider
Vl
'"
Square
Control
6
-2
Wave OUI
Vl
'"
'1';>
DVO-DV2
"-
Registers A, B, C, D
(4 Bytes)
Bus
Interface
k;=
~
Clock/
A
~
Clock, Alarm,
Calendar
Calendar RAM
Update
"
no Bytes)
BCDI
Binary
--
irleremen!
User RAM
(50 Bytes)
"-
)
v
Figure 2. MC146818 bus timing
AS
DS
R/W
ADO-
AD7
WRITE
ADO
AD7
READ
r-
VHIGH
----::;
-
VLOW
1+
-
~
...,
_~
r-
-
~
~~
\\\\\\\1'
I--
t<-'
:xx
-
~
NOTE: VHIGH= VOD- 2.0
v,
VLQw=o.a v, lor Veo =5.0 V ± 10%
7-6
k--
-
r--
-
t-;
IX
r--- _
"III
-
-
r-
I
-
P C-7200
CKOUT
CKFS
,....!
Hz
SOW
IRQ
RESET
PS