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AS1108

Datasheet - D e t a i l e d D e s c r i p t i o n

Shutdown Register (0xXC)

The Shutdown Register controls AS1108 shutdown mode (see Shutdown Mode on page 9).

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 13) 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 10 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 10 lists the code-B font; Table 11 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 12 shows the 1:1 pairing of each data bit and the appropriate segment line.

Figure 11. Standard 7-Segment LED Intensity Control and Inter-Digit Blanking

Table 8. 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

X

X

X

X

X

X

0

Shutdown Mode, Feature Register Unchanged

0x80

1

X

X

X

X

X

X

0

Normal Operation,

Reset Feature Register to Default Settings

0x01

0

X

X

X

X

X

X

1

Normal Operation, Feature Register Unchanged

0x81

1

X

X

X

X

X

X

1

Table 9. 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

X

X

X

X

0

0

0

0

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

0x01

X

X

X

X

0

0

0

1

Code-B/HEX decode for digits 3:0

0xFF

X

X

X

X

1

1

1

1

Table 10. 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

0

0

0

0

1

1

1

1

1

1

0

1

X

0

0

0

1

0

1

1

0

0

0

0

2

X

0

0

1

0

1

1

0

1

1

0

1

3

X

0

0

1

1

1

1

1

1

0

0

1

4

X

0

1

0

0

0

1

1

0

0

1

1

5

X

0

1

0

1

1

0

1

1

0

1

1

A

B

G

F

E

D

C

DP