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AS1108

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

8 Detailed Description

Serial-Addressing Format

Programming the AS1108 is accomplished by writing to the device’s internal registers (see Digit- and Control-Registers

on page 8) via the 4-wire serial interface. A programming sequence consists of 16-bit packages as depicted in Table 6.

The data is shifted into the internal 16-bit register with the rising edge of the CLK signal. With the rising edge of the

LOAD/CSN signal the data is latched into a digit- or control-register. The LOAD/CSN signal must go high after the 16th

rising clock edge.

The LOAD/CSN signal can also come later but this must happen just before the next rising edge of CLK, otherwise the

data will be lost. The contents of the internal shift register are applied 16.5 clock cycles later to pin DOUT. The data is

clocked out at the falling edge of CLK.

The first 4 bits (D15:D12) are “don't care” settings, bits D11:D8 contain the register address, and bits D7:D0 contain the

data. The first bit is D15, the most significant bit (MSB). The exact timing is shown in Figure 10.

Initial Power-Up

On initial power-up, the AS1108 registers are reset to their default values, the display is blanked, and the device goes

into shutdown mode. All registers should be programmed for normal operation at this time.

Note: The default settings enable only scanning of one digit; the internal decoder is disabled and the Intensity Control

Register (see page 11) is set to the minimum values.

Figure 10. Interface Timing

Table 6. 16-Bit Serial Data Format

D15

D14

D13

D12

D11

D10

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

X

X

X

X

Register Address (see Table 7) MSB

Data

LSB

LOAD/

CSN

CLK

DIN

DOUT

D15

D14

D1

D0