PCA9536_5

© NXP B.V. 2010. All rights reserved.

Product data sheet

Rev. 05 — 25 January 2010

4 of 22

NXP Semiconductors

PCA9536

6.

Functional description

Refer to Figure 1 “Block diagram of PCA9536”.

6.1 Registers

6.1.1 Command byte

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.

6.1.2 Register 0 - Input Port register

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.

The default ‘X’ is determined by the externally applied logic level, normally logic 1 when

no external signal externally applied because of the internal pull-up resistors.

Table 3.

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

Table 4.

Register 0 - Input Port register bit description

Legend: * default value

Bit

Symbol

Access

Value

Description

7

I7

read only

1*

not used

6

I6

read only

1*

5

I5

read only

1*

4

I4

read only

1*

3

I3

read only

X

determined by externally applied logic level

2

I2

read only

X

1

I1

read only

X

0

I0

read only

X