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AS1109

Datasheet - Detailed Descr i p ti on

8.6.3 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 10).

Figure 17. Detailed Shorted-LED Error Report Timing Diagram

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 14).

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:

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.

8.6.4 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 pattern 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 immediately increase to normal

levels and the detailed error report can be read out entering error-detection mode.

Input Data: 1 111 1111

11 1111 11

1 111 1111

111 111 11

1 1111 111

LED Status: 1 111 1X X 1

11 1111 11

1 111 1111

111 X 1 1 1 1

1 1111 111

Failure Code: 1 111 1001

11 1111 11

1 111 1111

111 011 11

1 1111 111

Global Flag Readout

Detailed Error Report Readout

SDI

OEN

LD

CLK

SDO

tH(L)

tSU(ERROR)

tP1

tSW(ERROR)

tP4

TFLAG

SFLAG

DBit6

DBit5

DBit4

DBit3

DBit2

DBit1

DBit0

Don’t

Care

Don’t

Care

SBit6

SBit5

SBit4

SBit3

SBit2

SBit1

SBit0

SBit7

New Data Input

Shorted-LED Error Report Output

OFLAG

TFLAG

tP4

tTESTING

Global Flag Readout

DBit7

For detailed timing information see Timing Diagrams on page 8.

tGSW(ERROR)

tGSW(ERROR)

tGSW(ERROR)