HT1621
Block Diagram
D
i
s
p
l
a
y
R
A
M
O
S
C
O
O
S
C
I
C
o
n
t
r
o
l
C
O
O
M
M
0
3
C
S
a
n
d
T
i
m
i
n
g
R
D
R
C
S
C
i
r
c
u
i
t
L
B
C
D
D
r
i
v
e
r
/
W
i
a
s
C
i
r
c
u
i
t
E
E
G
G
0
3
D
A
T
A
S
V
1
V
D
D
L
C
D
V
S
S
W
a
t
c
h
d
y
o
g
T
i
m
e
r
B
Z
T
o
n
e
F
r
e
q
u
e
n
c
a
n
d
I
R
Q
G
e
n
e
r
a
t
o
r
T
i
m
e
B
a
s
e
G
e
n
e
r
a
t
o
r
B
Z
Note: CS: Chip selection
BZ, BZ: Tone outputs
WR, RD, DATA: Serial interface
COM0~COM3, SEG0~SEG31: LCD outputs
IRQ: Time base or WDT overflow output
2
April 21, 2000