AS1123
Datasheet ꢀ Detailed Description
Detailed Open-LED Error Report
The detailed openꢀLED error report can be read out immediately after global error mode has been run. SDI must be 1 for the first device.
Figure 15. Detailed Open-LED Error Report Timing Diagram
Global Flag Readout
Detailed Error Report Readout
OEN
LD
tTESTING
tH(L)
tP4
tSU(ERROR)
tGSW(ERROR)
tGSW(ERROR)
CLK
SDI
tGSW(ERROR)
Don’t
Care
DBit14 DBit13 DBit12 DBitn DBit2 DBit1 DBit0
DBit15
tSW(ERROR)
New Data Input
Don’t
Care
OBit15 OBit14 OBit13 OBit12 OBitn OBit2 OBit1 OBit0
TFlag
tP4
OFlag
SDO
Open Error Report Output
tP1
For detailed timing information see Timing Diagrams on page 8.
Detailed OpenꢀLED Error Report Example:
Consider a case where three AS1123s are cascaded in one chain. A 1 indicates a LED is on, a 0 indicates a LED is off, and an X indicates an
open LED. The openꢀLED test is only applied to LEDs that are turned on. This test is used with a test pattern where all LEDs are on at test time.
IC1:[1111111111111111] IC2:[111XX11111111X11] IC3:[1111111111111111]
IC2 has three open LEDs switched on due to input. 3*16 clock cycles are needed to write the entire error code out. The detailed error report
would look like this:
Input Data: 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
LED Status: 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 X X 1 1 1 1 1 1 1 1 X 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
Failure Code: 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 1 1 1 1 1 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
Comparing this report with the input data indicates that IC2 is the device with two open LEDs at position 4 and 5 and one open LED at position
14. For such a test it is recommended to enter lowꢀcurrent diagnostic mode first (see LowꢀCurrent Diagnostic Mode on page 14) to reduce screen
flickering.
This test can be used also onꢀtheꢀfly without using an all 1s test pattern (see Figure 19 on page 16).
Note: In an actual report there are no spaces in the output. LEDs turned off during test time cannot be tested and will show a logic 1 in the
detailed error report.
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