Philips Semiconductors
Product specification
Remote 8-bit I/O expander for I
2
C-bus
CONTENTS
1
2
3
4
5
6
6.1
6.2
6.3
6.4
7
7.1
7.2
7.3
8
9
10
11
12
13
13.1
13.2
13.2.1
13.2.2
13.3
13.3.1
13.3.2
13.3.3
14
15
16
FEATURES
GENERAL DESCRIPTION
ORDERING INFORMATION
BLOCK DIAGRAM
PINNING
CHARACTERISTICS OF THE I
2
C-BUS
Bit transfer
Start and stop conditions
System configuration
Acknowledge
FUNCTIONAL DESCRIPTION
Addressing
Interrupt
Quasi-bidirectional I/Os
LIMITING VALUES
HANDLING
DC CHARACTERISTICS
I
2
C-BUS TIMING CHARACTERISTICS
PACKAGE OUTLINES
SOLDERING
Introduction
DIP
Soldering by dipping or by wave
Repairing soldered joints
SO and SSOP
Reflow soldering
Wave soldering
Repairing soldered joints
DEFINITIONS
LIFE SUPPORT APPLICATIONS
PURCHASE OF PHILIPS I
2
C COMPONENTS
PCF8574
1997 Apr 02
2
Philips Semiconductors
Product specification
Remote 8-bit I/O expander for I
2
C-bus
1
FEATURES
2
GENERAL DESCRIPTION
PCF8574
•
Operating supply voltage 2.5 to 6 V
•
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.
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.
The PCF8574 and PCF8574A versions differ only in their
slave address as shown in Fig.9.
3
ORDERING INFORMATION
PACKAGE
TYPE NUMBER
NAME
DESCRIPTION
plastic dual in-line package; 16 leads (300 mil)
plastic small outline package; 16 leads; body width 7.5 mm
plastic shrink small outline package; 20 leads; body width 4.4 mm
VERSION
SOT38-1
SOT162-1
SOT266-1
PCF8574P;
PCF8574AP
PCF8574T;
PCF8574AT
PCF8574TS
DIP16
SO16
SSOP20
1997 Apr 02
3
Philips Semiconductors
Product specification
Remote 8-bit I/O expander for I
2
C-bus
5
PINNING
PIN
SYMBOL
DIP16; SO16
A0
A1
A2
P0
P1
P2
P3
V
SS
P4
P5
P6
P7
INT
SCL
SDA
V
DD
n.c.
n.c.
n.c.
n.c.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
−
−
−
−
SSOP20
6
7
9
10
11
12
14
15
16
17
19
20
1
2
4
5
3
8
13
18
address input 0
address input 1
address input 2
quasi-bidirectional I/O 0
quasi-bidirectional I/O 1
quasi-bidirectional I/O 2
quasi-bidirectional I/O 3
supply ground
quasi-bidirectional I/O 4
quasi-bidirectional I/O 5
quasi-bidirectional I/O 6
quasi-bidirectional I/O 7
interrupt output (active LOW)
serial clock line
serial data line
supply voltage
not connected
not connected
not connected
not connected
DESCRIPTION
PCF8574
handbook, halfpage
INT
handbook, halfpage
1
2
3
4
5
PCF8574TS
6
7
8
9
20
19
18
17
16
15
14
13
12
11
MBD978
P7
P6
n.c.
P5
P4
VSS
P3
n.c.
P2
P1
A0
A1
A2
P0
P1
P2
P3
VSS
1
2
3
4
5
6
7
8
MBD979
16 VDD
15
14
PCF8574
PCF8574A
13
12
SDA
SCL
INT
P7
SCL
n.c.
SDA
VDD
A0
A1
n.c.
A2
11 P6
10
9
P5
P4
P0 10
Fig.2 Pin configuration (DIP16; SO16).
Fig.3 Pin configuration (SSOP20).
1997 Apr 02
5
Real-time operating system RTOS
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