HT1620 datasheet(8/16 Pages) HOLTEK

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HT1620

Rev. 1.80

July 27, 2009

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.

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 0

S E G 1

S E G 2

S E G 3

S E G 3 1

C O M 0

C O M 1

C O M 2

C O M 3

D 3

D 2

D 1

D 0

D a t a

A d d r

3 1

A d d r e s s 6 b i t s

( A 5 , A 4 , . . . , A 0 )

D a t a 4 b i t s

( D 3 , D 2 , D 1 , D 0 )

RAM Mapping

W D T E N / D I S

I R Q E N / D I S

C K

C L R W D T

C l o c k S o u r c e

/ 4

/ 2 5 6

T i m e B a s e

C L R T i m e r

I R Q

W D T

V D D

T I M E R E N / D I S

Timer and WDT Configurations

Name

Command Code

Function

LCD OFF

100 00000010X

Turn off LCD outputs

LCD ON

100 00000011X

Turn on LCD outputs

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

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