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Revision 1.34

10 - 15

AS1105

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

Display Test Register

With the display test register 0Fh all LED can be tested. In the test mode all LEDs are switched on at maximum

brightness (duty cycle 31/32). All programming of digit and control registers is maintained. The format of the register is

given in Table 13.

Note: The AS1105 remains in display-test mode until the display-test register is reconfigured for normal operation.

No-Op Register (Cascading of AS1105)

The no-operation register 00h is used when AS1105s are cascaded in order to support more than 4 digit displays. The

cascading must be done in a way that all DOUT are connected to DIN of the following AS1105. The LOAD and CLK

signals are connected to all devices. For a write operation for example to the fifth device the command must be

followed by four no-operation commands. When the LOAD signal finally goes to high all shift registers are latched. The

first four devices have got no-operation commands and only the fifth device sees the intended command and updates

its register.

Reset and external Clock Register

This register is addressed via the serial interface. It allows to switch the device to external clock mode (If D0=1 the

CLK pin of the serial interface operates as system clock input.) and to apply an external reset (D1). This brings all

registers (except reg. E) to default state. For standard operation the register contents should be "00h".

Table 12. Maximum segment current for 1-, 2-, or 3-digit displays

Number of Digits Displayed

Maximum Segment Current (mA)

110

220

330

Table 13. Display-test register format (address (hex) = 0xXF)

Mode

Register Data

D7

D6

D5

D4

D3

D2

D1

D0

Normal Operation

X

X

X

X

X

X

X

0

Display Test Mode

X

X

X

X

X

X

X

1

Table 14. Reset and external Clock register (address (hex) = 0xXE)

Mode

Address Code

(hex)

Register Data

D7

D6

D5

D4

D3

D2

D1

D0

Normal Operation, internal clock

0xXE

X

X

X

X

X

X

0

0

Normal Operation, external clock

0xXE

X

X

X

X

X

X

0

1

Reset state, internal clock

0xXE

X

X

X

X

X

X

1

0

Reset state, external clock

0xXE

X

X

X

X

X

X

1

1

1.5

2.0

2.5

3.0

3.5

40

12.2k

Ω

11.8k

Ω

11.0k

Ω

10.6k

Ω

9.69k

Ω

30

17.8k

Ω

17.1k

Ω

15.8k

Ω

15.0k

Ω

14.0k

Ω

20

29.8k

Ω

28.0k

Ω

25.9k

Ω

24.5k

Ω

22.6k

Ω

10

66.7k

Ω

63.7k

Ω

59.3k

Ω

55.4k

Ω

51.2k

Ω