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Revision 2.1

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AS1108

Data Sheet

Digit- and Control-Registers

Shutdown Register (0xXC)

The Shutdown Register controls AS1108 shutdown mode (see Shutdown Mode on page 7).

Decode Enable Register (0xX9)

The Decode Enable Register sets the decode mode. BCD/HEX decoding (either BCD code – characters 0:9, E, H, L,

P, and -, or HEX code – characters 0:9 and A:F) is selected by bit D2 (page 11) of the Feature Register. The Decode

Enable Register is used to select the decode mode or no-decode for each digit. Each bit in the Decode Enable Regis-

ter corresponds to its respective display digit (i.e., bit D0 corresponds to digit 0, bit D1 corresponds to digit 1 and so

on). Table 9 lists some examples of the possible settings for the Decode Enable Register bits.

Note: A logic high enables decoding and a logic low bypasses the decoder altogether.

When decode mode is used, the decoder looks only at the lower-nibble (bits D3:D0) of the data in the Digit-Registers,

disregarding bits D6:D4. Bit D7 sets the decimal point (SEG DP) independent of the decoder and is positive logic (bit

D7 = 1 turns the decimal point on). Table 9 lists the code-B font; Table 10 lists the HEX font.

When no-decode mode is selected, data bits D7:D0 of the Digit-Registers correspond to the segment lines of the

AS1108. Table 11 shows the 1:1 pairing of each data bit and the appropriate segment line.

Figure 10. Standard 7-Segment LED Intensity Control and Inter-Digit Blanking

Table 7. Shutdown Register Format (Address (HEX) = 0xXC))

Mode

HEX Code

Register Data

D7

D6

D5

D4

D3

D2

D1

D0

Shutdown Mode,

Reset Feature Register to Default Settings

0x00

0

XXXXXX

0

Shutdown Mode, Feature Register Unchanged

0x80

1

XXXXXX

0

Normal Operation,

Reset Feature Register to Default Settings

0x01

0

XXXXXX

1

Normal Operation, Feature Register Unchanged

0x81

1

XXXXXX

1

Table 8. Decode Enable Register Format (Address (HEX) = 0xX9))

Decode Mode

HEX Code

Register Data

D7

D6

D5

D4

D3

D2

D1

D0

No decode for digits 3:0

0x00

XXXX

0

0

0

0

Code-B/HEX decode for digit 0. No decode for digits 3:1

0x01

XXXX

0

0

0

1

Code-B/HEX decode for digits 3:0

0xFF

XXXX

1

1

1

1

Table 9. Code-B Font

7-Segment

Character

Register Data

On Segments = 1

D7

†

D6:D4

D3

D2

D1

D0

DP

†

A

B

C

D

E

F

G

0

X

00

00

11

11110

1

X

00

01

01

10000

2

X

00

10

11

01101

3

X

00

11

11

11001

4

X

01

00

01

10011

5

X

01

01

10

11011

A

B

G

F

E

D

C

DP