PATENTED
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
HT1620/HT1620G
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.
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
IR Q
C L R W D T
Timer and WDT Configurations
Name
LCD OFF
LCD ON
Command Code
100
00000010X
100
00000011X
Turn off LCD outputs
Turn on LCD outputs
Function
BIAS and COM
100
0010abXcX
c=0: 1/2 bias option
c=1: 1/3 bias option
ab=00: 2 commons option
ab=01: 3 commons option
ab=10: 4 commons option
Rev. 2.00
8
April 29, 2011
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
