PCA9552_5

© Koninklijke Philips Electronics N.V. 2006. All rights reserved.

Product data sheet

Rev. 05 — 9 March 2006

5 of 28

Philips Semiconductors

PCA9552

6.

Functional description

Refer to Figure 1 “Block diagram of PCA9552”.

6.1 Device address

Following a START condition, the bus master must output the address of the slave it is

accessing. The address of the PCA9552 is shown in Figure 5. To conserve power, no

internal pull-up resistors are incorporated on the hardware selectable address pins and

they must be pulled HIGH or LOW.

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.

6.2 Control Register

Following the successful acknowledgement of the slave address, the bus master will send

a byte to the PCA9552, which will be stored in the Control Register. This register can be

The lowest 3 bits are used as a pointer to determine which register will be accessed.

If the Auto-Increment flag (AI) is set, the four 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 ‘0000’ after the last

register is accessed.

When the Auto-Increment flag is set (AI = 1) and a read sequence is initiated, the

sequence must start by reading a register different from ‘0' (B3 B2 B1 B0

≠ 0000).

Only the 4 least significant bits are affected by the AI flag. Unused bits must be

programmed with zeroes.

Fig 5.

PCA9552 address

002aac169

1

1

0

0

A2

A1

A0 R/W

fixed

slave address

programmable

Reset state: 00h

Fig 6.

Control Register

002aac170

0

0

0

AI

B3

B2

B1

B0

register address

Auto-Increment flag