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TFT TV Service Manual 11/04/2006
11.19. PCF8574
11.19.1. General
Description
The PCF8574 is a silicon CMOS circuit. It provides general purpose remote I/O expansion for most
microcontroller families via the two-line bidirectional bus (I
2
C).The device consists of an 8-bit quasi-
bidirectional port and an I
2
C-bus interface. The PCF8574 has a low current consumption and includes
latched outputs with high current drive capability for directly driving LEDs. It also possesses an interrupt
line (INT) which can be connected to the interrupt logic of the microcontroller. By sending an interrupt
signal on this line, the remote I/O can inform the microcontroller if there is incoming data on its ports
without having to communicate via the I
2
C-bus. This means that the PCF8574 can remain a simple
slave device.
11.19.2. Features
• Operating supply voltage 2.5 to 6V
• Low standby current consumption of 10 µA maximum
• I
2
C to parallel port expander
• Open-drain interrupt output
• 8-bit remote I/O port for the I
2
C-bus
• Compatible with most microcontrollers
• Latched outputs with high current drive capability for directly driving LEDs
• Address by 3 hardware address pins for use of up to 8 devices (up to 16 with PCF8574A)
• DIP16, or space-saving SO16 or SSOP20 packages.
11.19.3. Pinning
