6

Data Sheet

AS2590

Rev. 1

Dec. 1993

BP0

BP1

BP2

BP3

S0

S1

Vss

Vss

Vss

Vss

Vss

Vss

Active Backplane

BP0

BP1

BP2

BP3

on

off

off

off

off

on

on

on

to high transition of the data line while the clock line is

high followed by a negative clock pulse indicates a stop

condition (see figure 4).

SDA

SCL

START

#1

LSB

B0

B1

B2

B3

MSB

B4

STOP

#1

WORD

GAP

START

#2

Figure 4 Interface Timing

Serial Interface

The serial interface is a one way, two line link between

the dialler (AS2574) and the display driver. The two lines

are the serial data line (SDA) and the serial clock line

(SCL). The display driver can only receive data.

Word Transfer:

Data are transferred as 5 bit words with start and stop bit.

the least significant bit is sent first after the start bit. As

long as there is no data transfer, both data and clock

lines have to remain high. Also between two words both

lines have to stay high for a specified time. Figure 4

shows the timing of the serial interface.

Start and Stop Conditions:

A start condition is detected when the data line goes

from high to low while the clock line is held high. A low

Figure 3 LCD driver outputs

Table 4 Codes for Serial Interface

NO SYMBOL MSB

B3

B2

B1

LSB HEX

1

SB0-on

00101

05

2

SB0-off

00011

03

3

SB1-on

10001

11

4

SB1-off

01001

09

5

SB2-on

00111

07

6

SB2-off

11111

1F

01011

0B

8

START

01101

0D

9

COPY

01111

0F

10

FIFO

10011

13

11

TIMER

10101

15

12

BLANK

11101

1D

13

TEST

10111

17

14

0

11100

1C

15

1

00000

00

16

2

00100

04

17

3

00010

02

18

4

10000

10

19

5

10100

14

20

6

10010

12

21

7

01000

08

22

8

01100

0C

23

9

01010

0A

24

a

00110

06

25

b

10110

16

26

c

01110

0E

27

d

11110

1E

28

*

11000

18

29

#

11010

1A

30

–

11011

1B

31

P/T

11001

19

32

r

00001

01