PCA9922BS NXP [NXP Semiconductors], PCA9922BS Datasheet - Page 9

• Manufacturer Part Number: PCA9922BS
• Description: 8-channel constant current LED driver with output error detection
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
PCA9922_1
Product data sheet
7.2.4 Setting the outputs to test
7.2.5 Capturing the fault/output error data
Before the Capture Fault sequence may be performed, the outputs must be set up. A logic
HIGH must be sent to the output control register for all eight bits. This is done after the
Enter Error Detect sequence is performed as a normal data load sequence as seen in
Figure
in the output control register (and the LED[7:0] pins). The output control register will have
to be restored to its proper values by the user after the error detect sequence has been
completed.
The Capture Fault/Error Data sequence can only follow the Enter Error Detect sequence.
If the Error Detect sequence has not occurred, this sequence will be treated as a normal
operational sequence. Once the Capture Fault sequence has occurred, an Exit Error
Detect sequence should be performed. There can be no more Capture Sequences until
another Enter Error Detect sequence has occurred.
The Capture Fault Sequence consists of holding OE LOW for no less than 3 clocks (CLK)
and for a minimum of 2 s, whichever is longer. During this period of time, the shift register
is being loaded with the fault status. As such, data presented to the device via SDI will not
be captured. Bit 7 of the fault data will be present on SDO by the first falling edge CLK
after the user de-asserts OE for this cycle. An error condition is output as a 1 (HIGH bit),
and a 0 (LOW bit) designates a normal status. Timing for this sequence is shown in
Figure
Fig 7.
5. Please note that this process is completely destructive to the data that is stored
7.
Timing for ‘Capture Fault Mode’ command
8-channel constant current LED driver with output error detection
Rev. 01 — 15 January 2009
OE = 1'b0 for minimum of 3 clocks
or 2 s, whichever is longer
SDO
CLK
OE
LE
previous serial data
fault data MSB
with fault data
resume shift
002aad205
PCA9922
© NXP B.V. 2009. All rights reserved.
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