Philips Semiconductors

Product data sheet

PCA9552

2004 Oct 01

6

PWM0 — PWM REGISTER 0

bit

7

6

5

4

3

2

1

0

default

1

0

0

0

0

0

0

0

The PWM0 register determines the duty cycle of BLINK0. The

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

PWM0 and HIGH when it is greater. If PWM0 is programmed with

00h, then the PWM0 output is always LOW.

The duty cycle of BLINK0 is:

256 – PWM0

256

PSC1 — FREQUENCY PRESCALER 1

bit

7

6

5

4

3

2

1

0

default

1

1

1

1

1

1

1

1

PSC1 is used to program the period of PWM output.

The period of BLINK1

+

(PSC1

) 1)

44

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 off) when the count is less than the value in

PWM1 and HIGH when it is greater. If PWM1 is programmed with

00h, then the PWM1 output is always LOW.

The duty cycle of BLINK1 is:

256 – PWM1

256

LS0 — LED 0–3 SELECTOR

LED 3

LED 2

LED 1

LED 0

bit

7

6

5

4

3

2

1

0

default

0

1

0

1

0

1

0

1

LS1 — LED 4–7 SELECTOR

LED 7

LED 6

LED 5

LED 4

bit

7

6

5

4

3

2

1

0

default

0

1

0

1

0

1

0

1

LS2 — LED 8–11 SELECTOR

LED 11

LED 10

LED 9

LED 8

bit

7

6

5

4

3

2

1

0

default

0

1

0

1

0

1

0

1

LS3 — LED 12–15 SELECTOR

LED 15

LED 14

LED 13

LED 12

bit

7

6

5

4

3

2

1

0

default

0

1

0

1

0

1

0

1

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

00 = Output is set LOW (LED on)

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

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 (01) 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 PCA9552 registers

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

EXTERNAL RESET

A reset can be accomplished by holding the RESET pin LOW for a

be held in their default state until the RESET input is once again

HIGH.

used.