HT1620_09 Datasheet, PDF (8/16 Pages) Holtek Semiconductor Inc – RAM Mapping 324 LCD Controller for I/O MCU

PATENTED
HT1620
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.
COM 3 COM 2 COM 1 COM 0
SEG 0
0
SEG 1
1
SEG 2
SEG 3
2
3
A d d r e s s 6 b its
(A 5 , A 4 , ..., A 0 )
S E G 31
D3
31
D2
D1
D0
D a ta 4 b its
(D 3 , D 2 , D 1 , D 0 )
A ddr
D a ta
RAM Mapping
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.
T im e B a s e
C lo c k S o u r c e
/2 5 6
T IM E R E N /D IS
IR Q
VDD
W D T E N /D IS
C L R T im e r
D
Q
W DT
/4
CK
R
IR Q E N /D IS
C LR W D T
Timer and WDT Configurations
Name
LCD OFF
LCD ON
Command Code
10000000010X
10000000011X
BIAS and COM
1000010abXcX
Function
Turn off LCD outputs
Turn on LCD outputs
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. 1.80
8
July 27, 2009