Philips Semiconductors

Product data sheet

PCA9533

2004 Oct 01

5

PWM1 — PWM REGISTER 1

bit

7

6

5

4

3

2

1

0

default

1

0

0

0

0

0

0

0

The PWM1 register determines the duty cycle of BLINK1. The

outputs are LOW (LED on) when the count is less than the value in

PWM1 and HIGH (LED off) when it is greater. If PWM1 is

programmed with 00h, then the PWM1 output is always HIGH

(LED off).

The duty cycle of BLINK1 is:

PWM1

256

LS0 — LED SELECTOR

LED3

LED2

LED 1

LED 0

bit

7

6

5

4

3

2

1

0

default

0

0

0

0

0

0

0

0

The LSx LED select registers determine the source of the LED data.

00 = Output is set Hi-Z (LED off – default)

01 = Output is set LOW (LED on)

10 = Output blinks at PWM0 rate

11 = Output blinks at PWM1 rate

PINS USED AS GENERAL PURPOSE I/Os

LED pins not used to control LEDs can be used as general purpose

I/Os.

For use as input: Set LEDx to high-impedance (00) and then read

the pin state via the input register.

For use as output: Connect external pull-up resistor to the pin and

size it according to the DC recommended operating characteristics.

LED output pin is HIGH when the output is programmed as

high-impedance, and LOW when the output is programmed LOW

through the “LED selector” register. The output can be pulse-width

controlled when PWM0 or PWM1 are used.

POWER-ON RESET

this point, the reset condition is released and the PCA9533 registers

are initialized to their default states, with all outputs in the off state.