AS1109
Data Sheet - Detailed Description
Detailed Shorted-LED Error Report
The detailed shorted-LED error report can be read out immediately after global error mode has been run (see Global
Error Mode on page 11).
Figure 17. Detailed Shorted-LED Error Report Timing Diagram
Global Flag Readout
Detailed Error Report Readout
OEN
LD
tTESTING
tSU(ERROR)
tH(L)
tP4
tGSW(ERROR)
tGSW(ERROR)
CLK
tGSW(ERROR)
Don’t
Care
DBit7
DBit6 DBit5 DBit4 DBit3 DBit2 DBit1 DBit0
New Data Input
SDI
tSW(ERROR)
SFLAG
Don’t
Care
SBit7
SBit6 SBit5 SBit4 SBit3 SBit2 SBit1 SBit0
OFLAG
TFLAG
TFLAG
SDO
Shorted-LED Error Report Output
tP4
tP1
For detailed timing information see Timing Diagrams on page 9.
Detailed Shorted-LED Error Report Example
Consider a case where five AS1109s are cascaded in one chain. A 1 indicates a LED is on, a 0 indicates a LED is off,
and an X indicates a shorted LED. This test is used with a test pattern where all LEDs are on at test time. Additionally,
this test should be run after starting low-current diagnostic mode (see Low-Current Diagnostic Mode on page 15).
IC1:[11111XX1] IC2:[11111111] IC3:[11111111] IC4:[111X1111] IC5:[11111111]
IC2 has two shorted LEDs and IC4 has one shorted LED switched on due to input. 5*8 clock cycles are needed to write
the entire error code out. The detailed error report would look like this:
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 X X 1 1 1 1 1 1 1 1 1 1 1 1 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 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1
Input Data:
LED Status:
Failure Code:
Showing IC1 as the device with two shorted LEDs at position 6 and 7, and IC4 with one shorted LED at position 4.
Note: In an actual report there are no spaces in the output. LEDs turned off during test time cannot be tested.
Low-Current Diagnostic Mode
To run the open- or shorted-LED test, a test pattern must be used that will turn on each LED to be tested. This test pat-
tern will cause a short flicker on the screen while the test is being performed. The low-current diagnostic mode can be
initiated prior to running a detailed error report to reduce this on-screen flickering.
Note: Normally, displays using such a diagnosis mode require additional cables, resistors, and other components to
reduce the current. The AS1109 has this current-reduction capability built-in, thereby minimizing the number of
external components required.
Low-current diagnostic mode can be initiated via 3 clock pulses during error-detection mode. After the falling edge of
LD, a test pattern displaying all 1s can be written to the shift register which will be used for the next error-detection test.
On the next falling edge of OEN, current is reduced to ILC. With the next rising edge of OEN the current will immedi-
ately increase to normal levels and the detailed error report can be read out entering error-detection mode.
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