AS1109
Data Sheet - Application Information
Low-current diagnosis mode is started with 3 clock pulses during error detection mode. After the three pulses of CLK,
a pulse of LD loads the internal all 1s test pattern. Then OEN should be enabled for 2µs for testing. With the rising
edge of OEN the test of the LEDs is stopped and while LD is high the desired error mode can be selected with the cor-
responding clock pulses.
With the next data input the detailed error code will be clocked out at SDO.
Note: See Figure 22 for the use of an external test pattern.
Figure 22. Low-Current Diagnosis Mode with External Test Pattern – 128 Cascaded AS1109s
2µs Low-Current Diagnosis Mode
Display
Data1
Data2
Data3
SDI
External all 1s Test Pattern
Data2
T/O or S Error Code
Data0
O or S Error Code
from Test Pattern
Temperature Error Code
SDO
GEF
GEF
3x Clocks
Low-Current
Mode
ClockforError
Mode 1x/2x
CLK
1024x
1024x
1024x
Rising Edge of OEN
Acquisition of Error Status
OEN
Falling Edge of LD; Error Register
is copied into Shift Register
LD
Current
≤ 100mA
≤ 100mA
≤ 0.8mA
GEF = Global Error Flag
Cascading Devices
To cascade multiple AS1109 devices, pin SDO must be connected to pin SDI of the next AS1109 (see Figure 23). At
each rising edge of CLK the LSB of the shift register will be written into the shift register SDI of the next AS1109 in the
chain. Data at the SDI pin is clocked in at the rising edge of the CLK pulse and is clocked out at the SDO pin 8.5 clock
cycles later at the falling edge of the CLK pulse.
Note: When n*AS1109 devices are in one chain, n*8 clock pulses are needed to latch-in the input data.
Figure 23. Cascading AS1109 Devices
SDI
AS1109 #1
AS1109 #2
AS1109 #n-1
SDI
SDO SDI
SDO
SDI
SDO
CLK
LD
OEN
CLK
LD
OEN
CLK
LD
OEN
CLK
LD
OEN
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