pca9901 NXP Semiconductors, pca9901 Datasheet - Page 5

• Manufacturer Part Number: pca9901
• Description: One Wire Single Led Driver
• Manufacturer: NXP Semiconductors

NXP Semiconductors
8. Functional description
PCA9901_1
Product data sheet
8.1 Digital interface overview - CTRL pin
Refer to
The digital interface is a simple one-wire uni-directional interface allowing the host
controller device to:
The lighting sequence to be captured by the PCA9901 contains the actual LED ON
(CTRL = 1) and LED OFF (CTRL = 0) timings. A sequence includes up to 3 different
patterns, each one containing one ON and one OFF value. Up to 3 LED ON and
3 LED OFF times can then be memorized by the PCA9901.
Commands are specific events that tell the PCA9901 what action needs to be performed.
The different commands are:
The PCA9901 decodes the commands using a 1.5 ms window from the first LOW to HIGH
transition that occurs on the CTRL pin. The following command or the data following a
command must then be issued at least 1.5 ms after.
At the end of the 1.5 ms window:
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•
•
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TRAINING START: Beginning of the training sequence. Upon reception of this
command, the PCA9901 starts capturing the lighting sequence.
TRAINING END: End of the training sequence. Upon reception of this command, the
capture stops, and the sequence is stored in the corresponding registers. The PCA9901
goes to Shutdown mode.
RUN ONCE: The sequence that has been memorized is executed once and then the
PCA9901 goes to Shutdown mode. If no sequence has been previously captured, the
PCA9901 goes to Shutdown mode.
RUN: The sequence that has been memorized is executed until a STOP Command
occurs.
STOP: The LED output is switched off at the end of the current LED ON time and the
PCA9901 goes to Shutdown mode.
RESET: The PCA9901 is reset and all the internal registers default to zeroes. The
PCA9901 goes to Shutdown mode.
send the lighting sequence to the LEDOUT pin and request the PCA9901 to capture
and memorize it at the same time
send the specific commands to execute the captured and memorized sequence later
reset the PCA9901 to a known state at any time.
The PCA9901 is fully operational (in the case the command is issued while the
PCA9901 was in Shutdown mode)
The command has been successfully decoded and the PCA9901 is ready for the next
message from the host controller (which will start at the next LOW to HIGH transition
on the CTRL pin), or is ready to execute the required command.
Figure 2 “Block diagram of
Rev. 01 — 3 December 2009
PCA9901”.
One wire single LED driver
PCA9901
© NXP B.V. 2009. All rights reserved.
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