AS1105
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 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
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. Timing Diagram
t
CS
LOAD
t
C
t
C
CLK
t
D
t
D
DIN
D15
D14
D1
t
D
DOUT
D0
t
C
t
C
t
LDC
Table 4. Serial Data Format (16 Bits)
D15
X
D14
X
D13
X
D12
X
D11
D10
D9
D8
D7
MSB
D6
D5
D4
D3
Data
D2
D1
D0
LSB
Address
Digit and Control Registers
The AS1105 incorporates 12 registers, which are listed in
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.
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 V
DD
,
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.
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