PCA9570DP datasheet(9/32 Pages) NXP

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PCA9570

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Product data sheet

Rev. 4 — 17 September 2014

9 of 32

NXP Semiconductors

PCA9570

Remote 4-bit general purpose outputs for 1 MHz I2C-bus

8.3 Reading from a port (Input mode)

All ports are outputs and cannot be used as inputs. When reading the device, the data

returned is the port state at the pin. To read, the master (microcontroller) first addresses

the slave device by setting the last bit of the byte containing the slave address to logic 1.

The data byte that follows on the SDA is the value of the ports pins. There is no limit to the

number of bytes read, and the state of the output port pins is updated at each

acknowledge cycle. Logic 1 means that the port is HIGH. Logic 0 means that the port is

LOW. When the PCA9570 is read, P7 through P4 return logic ‘1’.

8.4 Power-on reset

When power is applied to VDD, an internal Power-On Reset (POR) holds the device in a

reset condition until VDD has reached VPOR. At that point, the reset condition is released

and the device registers and I2C-bus/SMBus state machine initialize to their default states.

See Section 14 for DC and AC characteristics of the POR function.

Fig 12. Write mode (output)

A5 A4 A3 A2 A1 A0

SA6

slave address

START condition

R/W

acknowledge

from slave

002aag833

P6 P5

data 1

acknowledge

from slave

12345678

SCL

SDA

acknowledge

from slave

write to port

data output from port

tv(Q)

data 2

DATA 2 VALID

P4 P3

P1 P0

P4 P3

P1 P0

tv(Q)

DATA 1 VALID

P2 output voltage

Fig 13. Read input port register

A5 A4 A3 A2 A1 A0

SA6

slave address

START condition

R/W

acknowledge

from slave

002aag846

data from port

acknowledge

from master

SDA

no acknowledge

from master

read from

port

data from port

DATA 1

DATA 4

STOP

condition

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