pca8574 NXP Semiconductors, pca8574 Datasheet - Page 12

• Manufacturer Part Number: pca8574
• Description: Pca8574/pca8574a Remote 8-bit I/o Expander For I2c-bus With Interrupt
• Manufacturer: NXP Semiconductors

NXP Semiconductors
10. Application design-in information
PCA8574_PCA8574A_2
Product data sheet
10.1 Bidirectional I/O expander applications
10.2 High current-drive load applications
In the 8-bit I/O expander application shown in
P7 are outputs. When used in this configuration, during a write, the input (P0 and P1)
must be written as HIGH so the external devices fully control the input ports. The desired
HIGH or LOW logic levels may be written to the I/Os used as outputs (P2 to P7). During a
read, the logic levels of the external devices driving the input ports (P0 and P1) and the
previous written logic level to the output ports (P2 to P7) will be read.
The GPIO also has an interrupt line (INT) that can be connected to the interrupt logic of
the microprocessor. By sending an interrupt signal on this line, the remote I/O informs the
microprocessor that there is incoming data or a change of data on its ports without having
to communicate via the I
The GPIO has a maximum sinking current of 25 mA per bit. In applications requiring
additional drive, two port pins in the same octal may be connected together to sink up to
50 mA current. Both bits must then always be turned on or off together. Up to 8 pins (one
octal) can be connected together to drive 200 mA.
Fig 15. Bidirectional I/O expander application
Fig 16. High current-drive load application
PROCESSOR
CORE
PROCESSOR
CORE
Rev. 02 — 14 May 2007
2
C-bus.
V
DD
V
DD
Remote 8-bit I/O expander for I
SDA
SCL
INT
AD0
AD1
AD2
V
SDA
SCL
INT
AD0
AD1
AD2
DD
Figure
V
P0
P1
P2
P3
P4
P5
P6
P7
DD
15, P0 and P1 are inputs, and P2 to
P0
P1
P2
P3
P4
P5
P6
P7
temperature sensor
battery status
control for latch
control for switch
control for audio
control for camera
control for MP3
PCA8574/74A
002aac124
LOAD
V
2
DD
C-bus with interrupt
002aac123
V
© NXP B.V. 2007. All rights reserved.
DD
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