AS1108
Datasheet - Detailed Description
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 9) 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.
Table 6. 16-Bit Serial Data Format
D15 D14 D13 D12
D11
D10
D9
D8
D7
D6
D5
D4
Data
D3
D2
D1
D0
X
X
X
X
Register Address (see Table 7) MSB
LSB
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 12) is set to the minimum values.
Figure 10. Interface Timing
LOAD/
CSN
tCSW
tCSH
tCP
tCSS
tLDCK
tCL
tCH
CLK
DIN
t
DH
t
DS
D15
D14
D1
D0
tDO
DOUT
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