PATENTED
HT1621/HT1621G
Application Circuits
Host Controller with an HT1621 Display System
C
R
S
D
V
D
D
*
*
V
R
W
D
R
V
L
C
D
A
T
A
M
C
U
H
T
1
6
2
1
B
*
B
Z
R
P
i
e
z
I
R
Q
C
l
o
c
k
O
u
t
B
Z
O
O
S
S
C
C
I
O
C
O
M
0
~
C
O
M
3
S
E
G
0
~
S
E
E
E
x
x
t
t
e
e
r
r
n
n
a
a
l
l
C
C
o
o
l
l
c
c
k
k
1
2
O
n
-
c
h
i
p
O
S
C
1
/
2
o
r
1
/
3
B
i
a
s
;
1
/
2
,
1
/
C
r
y
s
t
a
l
L
C
D
P
a
n
e
l
3
2
7
6
8
H
z
C
1
C
2
Note: The connection of IRQ and RD pin can be selected depending on the requirement of the MCU.
The voltage applied to VLCD pin must be equal to or lower than VDD
.
Adjust VR to fit LCD display, at VDD=5V, VLCD=4V, VR=15kW±20%.
Adjust R (external pull-high resistance) to fit user¢s time base clock.
In order to obtain the correct frequency, two additional load capacities (C1, C2) are needed. The value of the
capacity depends on how accurate the crystal is. We suggest that you can follow the table, which suggests the
value of capacities.
The table illustrates the suggestion value of capacities (C1,C2)
Crystal Error
±10ppm
Capacity Value
0~10p
10~20ppm
10~20p
Command Summary
Name
READ
ID
Command Code
D/C
D
Function
Read data from the RAM
Write data to the RAM
Def.
1 1 0 A5A4A3A2A1A0D0D1D2D3
1 0 1 A5A4A3A2A1A0D0D1D2D3
WRITE
D
READ-MODIFY-
WRITE
1 0 1 A5A4A3A2A1A0D0D1D2D3
1 0 0 0000-0000-X
D
C
READ and WRITE to the RAM
Turn off both system oscillator and LCD
bias generator
SYS DIS
Yes
Yes
SYS EN
1 0 0 0000-0001-X
1 0 0 0000-0010-X
1 0 0 0000-0011-X
1 0 0 0000-0100-X
1 0 0 0000-0101-X
1 0 0 0000-0110-X
1 0 0 0000-0111-X
C
C
C
C
C
C
C
Turn on system oscillator
LCD OFF
LCD ON
Turn off LCD bias generator
Turn on LCD bias generator
Disable time base output
TIMER DIS
WDT DIS
TIMER EN
WDT EN
Disable WDT time-out flag output
Enable time base output
Enable WDT time-out flag output
Rev. 3.10
13
November 5, 2012
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
