HT1647

Rev. 1.40

8

November 9, 2010

PATENTED

S E G 0

S E G 1

S E G 2

S E G 3

S E G 6 3

C O M 1 4

C O M 1 5

A d d r

5 1 1

7

2 3

3 1

C O M 0

C O M 1

D 0

D a t a

A d d r

5 0 4

0

8

2 4

D a t a 4 B i t s

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

A d d r e s s 9 B i t s

( A 8 , A 7 , . . . . , A 0 )

1 6

D 1

D 2

D 3

D a t a

D 0

D 1

D 2

D 3

1 5

: T w o b i t s o f R A M m a p t o L C D ' s o n e p i x e l a n d d e c i d e 4 - l e v e l g r a y s c a l e

o r 4 - c o l o r d i s p l a y c o n c u r r e n t l y .

Display Memory

- RAM Structure

Gray Scale Level Decision

HT1647 uses PWM technique to provide 4-level gray

scale display. Two bits of RAM data code ((D3, D2) or

(D1, D0)) decide one pixel level of LCDs, level 1~level

divided by 4. Every level must be defined as one kind of

gray scale by PWM data (namely B4~B0) previously.

RAM Data Code

(D3, D2) or (D1, D0)

Choice Gray Scale Level

(1, 1)

Level 1

(1, 0)

Level 2

(0, 1)

Level 3

(0, 0)

Level 4

RAM Data Defined Gray Scale Level

Frame Frequency

HT1647 provides two kinds of frame frequency option

by command code; 89Hz and 170Hz respectively.

FRAME 89Hz provides 89Hz frame frequency and ac-

tive segment signal width can be divided into 24 sec-

tions concurrently. FRAME 170Hz provides 170Hz

frame frequency and active segment signal width can be

divided into 13 sections concurrently. The 24 sections

display a particularly gray scale more than the 13 sec-

tions by PWM data. The default is FRAME 89Hz.

Gray Scale Display

If the user choose 89Hz frame frequency, a max. of 24

sections can be programmed to suit a satisfactory gray

scale in every level. Similarly, if the user choose 170Hz

frame frequency, a max. of 13 sections can be pro-

grammed to suit a satisfactory gray scale in every level.

HT1647 provides 5-bit PWM data to control the length of

the section. In other words, a max. Of 24 gray scales are

generated by 5-bit binary PWM data. At FRAME 89Hz

mode, the HT1647 only provides a max. of 24 adjust-

able gray scales although 32 is the expressed max.

value by 5 bits binary code. When 5 bits binary code

value is more than 23, the PWM control circuit uniformly

regards 23. To increase PWM data indicates to increase

the length of the active segment signal. The varied

length of the active segment signal displays varied gray

scale in TN-type, STN-type LCDs (refer to table 1). Simi-

larly, it displays varied color in ECB-type LCDs. The

color display is derived from ECB-type LCD specifica-

tion. At FRAME 170Hz mode, the HT1647 only provides

a max. of 13 adjustable gray scales although 32 is the

expressed max. value by 5 bits binary code. When the 5

bits binary code value is more than 12, the PWM control

circuit uniformly regards 12. The user must appoint four

kinds of PWM data to four kinds of different gray scale

level by commanding PWM data (refer to table 2).

Name

Command Code

Function

FRAME 170Hz

X100-0001-1000-XXXX

Select 170Hz frame frequency and active segment signal

width can be divided into 13 sections

FRAME 89Hz

X100-0001-1101-XXXX

Select 89Hz frame frequency and active segment signal width

can be divided into 24 sections

Frame Frequency Selection Command Code