PCA9901_1

© NXP B.V. 2009. All rights reserved.

Product data sheet

Rev. 01 — 3 December 2009

5 of 27

NXP Semiconductors

PCA9901

One wire single LED driver

8.

Functional description

Refer to Figure 2 “Block diagram of PCA9901”.

8.1 Digital interface overview - CTRL pin

The digital interface is a simple one-wire uni-directional interface allowing the host

controller device to:

and memorize it at the same time

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:

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.

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:

PCA9901 was in Shutdown mode)

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.