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AS1105

Datasheet - Detailed Descr i p ti on

8 Detailed Description

8.1 Serial-Addressing Modes

The programming of the AS1105 is done via the 4-wire serial interface. A programming sequence consists of 16-bit packages. 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 signal, the data is latched into a digital or

control register depending on the address. The LOAD signal must go to high after the 16th rising clock edge. The LOAD signal can also come

later but just before the next rising edge of CLK, otherwise data would be lost. The content of the internal shift register is applied 16.5 clock

cycles later to the DOUT pin. The data is clocked out at the falling edge of CLK. The Bits of the 16Bit-programming package are described in

Table 4. The first 4 Bits D15-D12 are ”don’t care, D11-D8 contain the address and D7-D0 contain the data. The first bit is D15, the most

significant bit (MSB). The exact timing is given in Figure 5.

Figure 5. Timing Diagram

8.2 Digit and Control Registers

The AS1105 incorporates 12 registers, which are listed in Table 5. The digit and control registers are selected via the 4Bit address word. The 4

digit registers are realized with a 32bit memory. Each digit can be controlled directly without rewriting the whole contents. The control registers

consist of decode mode, display intensity, number of scanned digits, shutdown, display test and reset/external clock register.

8.3 Shutdown Mode

The AS1105 features a shutdown mode, where it consumes only 20µA current. The shutdown mode is entered via a write to register 0Ch. Then

all segment current sources are pulled to ground and all digit drivers are connected to VDD, so that nothing is displayed. All internal digit

registers keep the programmed values. The shutdown mode can either be used for power saving or for generating a flashing display by

repeatedly entering and leaving the shutdown mode. The AS1105 needs typically 250µs to exit the shutdown mode. During shutdown, the

AS1105 is fully programmable. Only the display test function overrides the shutdown mode.

Table 4. Serial Data Format (16 Bits)

D15

D14

D13

D12

D11

D10

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

X

X

X

X

Address

MSB

Data

LSB

D0

D1

D15

D14

DOUT

DIN

CLK

LOAD

tCSW

tCL

tC

tC

tC

tLDCK

tDO

tD

tD