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  D T SHEET Product specificationSupersedes data of September 1994File under Integrated Circuits, IC121997Apr02 INTEGRATED CIRCUITS  PCF8574 Remote 8-bit I/O expander forI 2 C-bus  1997Apr022 Philips SemiconductorsProduct specification Remote 8-bit I/O expander for I 2 C-busPCF8574 CONTENTS 1FEATURES2GENERAL DESCRIPTION3ORDERING INFORMATION4BLOCK DIAGRAM5PINNING6CHARACTERISTICS OF THE I 2 C-BUS6.1Bit transfer6.2Start and stop conditions6.3System configuration6.4Acknowledge7FUNCTIONAL DESCRIPTION7.1Addressing7.2Interrupt7.3Quasi-bidirectional I/Os8LIMITING VALUES9HANDLING10DC CHARACTERISTICS11I 2 C-BUS TIMING CHARACTERISTICS12PACKAGE OUTLINES13SOLDERING13.1Introduction13.2DIP13.2.1Soldering by dipping or by wave13.2.2Repairing soldered joints13.3SO and SSOP13.3.1Reflow soldering13.3.2Wave soldering13.3.3Repairing soldered joints14DEFINITIONS15LIFE SUPPORT APPLICATIONS16PURCHASE OF PHILIPS I 2 C COMPONENTS  1997Apr023Philips SemiconductorsProduct specification Remote 8-bit I/O expander for I 2 C-busPCF8574 1FEATURES ã Operating supply voltage 2.5to6V ã Low standby current consumption of 10  µ A maximum ã I 2 C to parallel port expander ã Open-drain interrupt output ã 8-bit remote I/O port for the I 2 C-bus ã Compatible with most microcontrollers ã Latched outputs with high current drive capability fordirectly driving LEDs ã Address by 3 hardware address pins for use of up to8devices (up to 16 with PCF8574A) ã DIP16, or space-saving SO16 or SSOP20 packages. 2GENERAL DESCRIPTION The PCF8574 is a silicon CMOS circuit. It provides generalpurpose remote I/O expansion for most microcontrollerfamilies via the two-line bidirectional bus (I 2 C).The device consists of an 8-bit quasi-bidirectional port andan I 2 C-bus interface. The PCF8574 has a low currentconsumption and includes latched outputs with highcurrent drive capability for directly driving LEDs. It alsopossesses an interrupt line (INT) which can be connectedto the interrupt logic of the microcontroller. By sending aninterrupt signal on this line, the remote I/O can inform themicrocontroller if there is incoming data on its ports withouthaving to communicate via the I 2 C-bus. This means thatthe PCF8574 can remain a simple slave device.The PCF8574 and PCF8574A versions differ only in theirslave address as shown in Fig.9. 3ORDERING INFORMATIONTYPE NUMBERPACKAGENAMEDESCRIPTIONVERSION PCF8574P;PCF8574APDIP16plastic dual in-line package; 16leads (300mil)SOT38-1PCF8574T;PCF8574ATSO16plastic small outline package; 16leads; body width 7.5mmSOT162-1PCF8574TSSSOP20plastic shrink small outline package; 20leads; body width 4.4mmSOT266-1  1997Apr024Philips SemiconductorsProduct specification Remote 8-bit I/O expander for I 2 C-busPCF8574 4BLOCK DIAGRAM Fig.1 Block diagram (SOT38-1 and SOT162-1). handbook, full pagewidth  MBD980  I C BUSCONTROL 2 INPUTFILTER1231415   13INTERRUPTLOGIC12P711P610P59P47P36P25P14P08 BITI/OPORTSHIFTREGISTERLP FILTERWRITE pulseREAD pulsePOWER-ONRESET168VDDVSSSDASCLA2A1A0INT PCF8574
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