Philips Semiconductors

Product data sheet

PCA9561

2004 May 17

4

DEVICE ADDRESS

Following a START condition the bus master must output the

address of the slave it is accessing. The address of the PCA9561 is

shown in Figure 1. 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 slave 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.

0

0

1

A1

A0

R/W

11

SW00955

MSB

LSB

FIXED

PROGRAMMABLE

Figure 1. Slave address

CONTROL REGISTER

Following the successful acknowledgement of the slave address,

the bus master will send a byte to the PCA9561, which will be stored

in the control register. This register can be written and read via the

SW00954

D7

D6

D5

D4

D3

D2

D1

D0

Figure 2. Control Register

CONTROL REGISTER DEFINITION

Following the address and acknowledge bit with logic 0 in the read/write bit, the first byte written is the command byte. If the command byte is

reserved and therefore not valid, it will not be acknowledged. Only valid command bytes will be acknowledged.

Table 1. Register Addresses

D7

D6

D5

D4

D3

D2

D1

D0

REGISTER

NAME

TYPE

REGISTER

FUNCTION

0

0

0

0

0

0

0

0

EEPROM 0

Read/Write

EEPROM byte 0

register

0

0

0

0

0

0

0

1

EEPROM 1

Read/Write

EEPROM byte 1

register

0

0

0

0

0

0

1

0

EEPROM 2

Read/Write

EEPROM byte 2

register

0

0

0

0

0

0

1

1

EEPROM 3

Read/Write

EEPROM byte 3

register

1

1

1

1

1

1

1

1

MUX_IN

Read

MUX_IN values

register

Table 2. Commands

D7

D6

D5

D4

D3

D2

D1

D0

COMMAND

1

1

1

1

1

0

0

0

MUX_OUT from EEPROM byte 0

1

1

1

1

1

1

0

0

MUX_OUT from EEPROM byte 1

1

1

1

1

1

0

X

1

MUX_OUT from EEPROM byte 2

1

1

1

1

1

1

X

1

MUX_OUT from EEPROM byte 3

1

1

1

1

1

X

1

0

MUX_OUT from MUX_IN

1

1

1

1

1

X

X

1

NOTE:

1. All other combinations are reserved.

2. MUX_SELECT pins select between MUX_IN and EEPROM to MUX_OUT.