HT1620
t
f
W R , R D
C lo c k
9 0 %
5 0 %
1 0 %
t
r
V
t
C
L K
D D
V A L ID D A T A
D B
V
t
h
u
D D
t
C
G N D
5 0 %
t
s
G N D
V
D D
L K
W R , R D
C lo c k
5 0 %
G N D
Figure 1
Figure 2
t
C
S
C S
5 0 %
t
s
u 1
V
D D
t
h
1
G N D
V
D D
W R , R D
C lo c k
5 0 %
F IR S T
C lo c k
L A S T
C lo c k
G N D
Figure 3
Functional Description
Display Memory
-
RAM structure
The static display RAM is organized into 32´4 bits and
stores the display data. The contents of the RAM are di-
rectly mapped to the contents of the LCD driver. Data in
the RAM can be accessed by the READ, WRITE and
READ-MOD IFY-WRITE commands. The following is a
mapping from the RAM to the LCD patterns.
C O M 3
S E G 0
S E G 1
S E G 2
S E G 3
3
2
A d d r e s s 6 b its
(A 5 , A 4 , ..., A 0 )
1
C O M 2
C O M 1
C O M 0
0
Time Base and Watchdog Timer
-
WDT
The time base generator and WDT share the same di-
vided (¸256) counter. TIMER DIS/EN/CLR, WDT
DIS/EN/CLR and IRQ EN/DIS are independent from
each other. Once the WDT time-out occurs, the IRQ pin
will stay at a logic low level until the CLR WDT or the
IRQ DIS command is issued.
Buzzer Tone Output
A simple tone generator is implemented in the HT1620.
The tone generator can output a pair of differential driv-
ing signals on the BZ and BZ which are used to gener-
ate a single tone.
LCD Driver
The HT1620 is a 128 (32´4) pattern LCD driver. It can be
configured as 1/2 or 1/3 bias and 2 or 3 or 4 commons of
LCD driver by the S/W configuration. This feature
makes the HT1620 suitable for multiple LCD applica-
tions. The LCD driving clock is derived from the system
clock. The value of the driving clock is always 256Hz even
when it is at a 32.768kHz crystal oscillator frequency. The
LCD corresponding commands are summarized in the ta-
ble.
IR Q
S E G 3 1
D
3
D 2
D
1
D
0
3 1
A d d r
D a ta
D a ta 4 b its
(D 3 , D 2 , D 1 , D 0 )
RAM Mapping
T im e B a s e
C lo c k S o u r c e
/2 5 6
V D D
C L R
T im e r
W D T
/4
D
C K
R
T IM E R
E N /D IS
W D T E N /D IS
Q
IR Q
E N /D IS
C L R
W D T
Timer and WDT Configurations
Rev. 1.30
6
March 27, 2007
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
