Philips Semiconductors

Objective data sheet

PCA9536

2004 Aug 20

4

REGISTERS

Command Byte

Command

Protocol

Function

0

Read byte

Input port register

1

Read/write byte

Output port register

2

Read/write byte

Polarity inversion register

3

Read/write byte

Configuration register

The command byte is the first byte to follow the address byte during

a write transmission. It is used as a pointer to determine which of the

following registers will be written or read.

Register 0 – Input Port Register

bit

X

X

X

X

I3

I2

I1

I0

default

1

1

1

1

1

1

1

1

This register is a read only port. It reflects the incoming logic levels

of the pins, regardless of whether the pin is defined as an input or an

output by Register 3. Writes to this register have no effect.

“X” are “don’t care” bits and can be programmed with either “0”

or “1”.

Register 1 – Output Port Register

bit

X

X

X

X

O3

O2

O1

O0

default

1

1

1

1

1

1

1

1

This register reflects the outgoing logic levels of the pins defined as

outputs by Register 3. Bit values in this register have no effect on

pins defined as inputs. Reads from this register return the value that

is in the flip-flop controlling the output selection, NOT the actual pin

value.

“X” are “don’t care” bits and can be programmed with either “0”

or “1”.

Register 2 – Polarity Inversion Register

bit

X

X

X

X

N3

N2

N1

N0

default

0

0

0

0

0

0

0

0

This register allows the user to invert the polarity of the Input Port

Register data. If a bit in this register is set (written with ‘1’), the

corresponding Input Port data is inverted. If a bit in this register is

cleared (written with a ‘0’), the Input Port data polarity is retained.

“X” are “don’t care” bits and can be programmed with either “0”

or “1”.

Register 3 – Configuration Register

bit

X

X

X

X

C3

C2

C1

C0

default

1

1

1

1

1

1

1

1

This register configures the directions of the I/O pins. If a bit in this

register is set, the corresponding port pin is enabled as an input with

high impedance output driver. If a bit in this register is cleared, the

corresponding port pin is enabled as an output. At reset, the I/Os are

“X” are “don’t care” bits and can be programmed with either “0”

or “1”.

Power-on Reset

point, the reset condition is released and the PCA9536 registers and

must be lowered below 0.2 V to reset the device.

restored to the operating voltage.