Philips Semiconductors

Product data sheet

PCA9553

2004 Oct 01

4

DEVICE ADDRESSING

Following a START condition the bus master must output the

address of the slave it is accessing. The address of the PCA9553/01

is shown in Figure 3 and PCA9553/02 in Figure 4.

11

0

0

0

1

0

SLAVE ADDRESS

SW01037

R/W

Figure 3. Slave address — PCA9553/01

11

0

0

0

1

1

SLAVE ADDRESS

SW01038

R/W

Figure 4. Slave address — PCA9553/02

The last bit of the address byte defines the operation to be

performed. When set to logic 1 a read is selected, while a logic 0

selects a write operation.

CONTROL REGISTER

Following the successful acknowledgement of the slave address,

the bus master will send a byte to the PCA9553 which will be stored

in the Control Register.

0

0

AI

B2

B1

B0

0

SW01034

0

AUTO-INCREMENT FLAG

REGISTER ADDRESS

RESET STATE: 00h

Figure 5. Control register

The lowest 3 bits are used as a pointer to determine which register

will be accessed.

If the auto-increment flag is set, the three low order bits of the

Control Register are automatically incremented after a read or write.

This allows the user to program the registers sequentially. The contents

of these bits will rollover to ‘000’ after the last register is accessed.

When auto-increment flag is set (AI = 1) and a read sequence is

initiated, the sequence must start by reading a register different from

‘0’ (B2 B1 B0

0 0 0 0)

Only the 3 least significant bits are affected by the AI flag.

Unused bits must be programmed with zeroes.

Control Register definition

B2

B1

B0

REGISTER

NAME

TYPE

REGISTER

FUNCTION

0

0

0

INPUT

READ

INPUT REGISTER

0

0

1

PSC0

READ/

WRITE

FREQUENCY

PRESCALER 0

0

1

0

PWM0

READ/

WRITE

PWM REGISTER 0

0

1

1

PSC1

READ/

WRITE

FREQUENCY

PRESCALER 1

1

0

0

PWM1

READ/

WRITE

PWM REGISTER 1

1

0

1

LS0

READ/

WRITE

LED SELECTOR

REGISTER DESCRIPTION

INPUT — INPUT REGISTER

LED

3

LED

2

LED

1

LED

0

bit

7

6

5

4

3

2

1

0

default

0

0

0

0

X

X

X

X

The INPUT register reflects the state of the device pins. Writes to

this register will be acknowledged but will have no effect.

NOTE: The default value “X” is determined by the externally applied

logic level, normally ‘1’ when used for directly driving LED with

PSC0 — FREQUENCY PRESCALER 0

bit

7

6

5

4

3

2

1

0

default

1

1

1

1

1

1

1

1

PSC0 is used to program the period of the PWM output.

The period of BLINK0

+

(PSC0

) 1)

44

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