Datasheet

DESCRIPTION/ORDERING INFORMATION (CONTINUED)
PCF8574
SCPS068G – JULY 2001 – REVISED MAY 2008 ............................................................................................................................................................... www.ti.com
The PCF8574 provides an open-drain output ( INT) that can be connected to the interrupt input of a
microcontroller. An interrupt is generated by any rising or falling edge of the port inputs in the input mode. After
time, t
iv
, INT is valid. Resetting and reactivating the interrupt circuit is achieved when data on the port is changed
to the original setting or data is read from, or written to, the port that generated the interrupt. Resetting occurs in
the read mode at the acknowledge bit after the rising edge of the SCL signal, or in the write mode at the
acknowledge bit after the high-to-low transition of the SCL signal. Interrupts that occur during the acknowledge
clock pulse can be lost (or be very short) due to the resetting of the interrupt during this pulse. Each change of
the I/Os after resetting is detected and, after the next rising clock edge, is transmitted as INT. Reading from, or
writing to, another device does not affect the interrupt circuit.
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. Therefore, the PCF8574 can remain a simple slave
device.
ORDERING INFORMATION
T
A
PACKAGE
(1) (2)
ORDERABLE PART NUMBER TOP-SIDE MARKING
PCF8574N
PDIP – N Tube of 25 PCF8574N
PCF8574NE4
QFN – RGT Reel of 3000 PCF8574RGTR ZWJ
PCF8574RGYR
QFN – RGY Reel of 1000 PF574
PCF8574RGYRG4
PCF8574DW
Tube of 40
PCF8574DWE4
SOIC – DW PCF8574
– 40 ° C to 85 ° C PCF8574DWR
Reel of 2000
PCF8574DWRE4
PCF8574PW
Tube of 70
PCF8574PWE4
TSSOP – PW PF574
PCF8574PWR
Reel of 2000
PCF8574PWRE4
PCF8574DGVR
TVSOP – DGV Reel of 2000 PF574
PCF8574DGVRE4
(1) Package drawings, thermal data, and symbolization are available at www.ti.com/packaging .
(2) For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI
website at www.ti.com .
2 Submit Documentation Feedback Copyright © 2001 – 2008, Texas Instruments Incorporated
Product Folder Link(s): PCF8574