Datasheet

PCA9672 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
Product data sheet Rev. 3 — 27 May 2013 11 of 36
NXP Semiconductors
PCA9672
Remote 8-bit I/O expander for Fm+ I
2
C-bus with interrupt and reset
8.2 Writing to the port (Output mode)
The master (microcontroller) sends the START condition and slave address setting the
last bit of the address byte to logic 0 for the write mode. The PCA9672 acknowledges and
the master then sends the data byte for P7 to P0 to the port register. As the clock line
goes HIGH, the 8-bit data is presented on the port lines after it has been acknowledged by
the PCA9672. If a LOW is written, the strong pull-down turns on and stays on. If a HIGH is
written, the strong pull-up turns on for
1
⁄
2
of the clock cycle, then the line is held HIGH by
the weak current source. The master can then send a STOP or ReSTART condition or
continue sending data. The number of data bytes that can be sent successively is not
limited and the previous data is overwritten every time a data byte has been sent and
acknowledged.
Ensure a logic 1 is written for any port that is being used as an input to ensure the strong
external pull-down is turned off.
Simple code for Write cycle:
<S> <slave address + W> <ACK> <DATA1> <ACK> <DATA2> <ACK> <DATA1> ...
<DATAn> <ACK> <P>
Fig 13. Write mode (output)
A5 A4 A3 A2 A1 A0 0 ASA6
slave address
START condition R/W
acknowledge
from slave
002aah623
P6 1P7
data 1
A
acknowledge
from slave
12345678SCL 9
SDA
A
acknowledge
from slave
write to port
data output from port
t
v(Q)
P5
data 2
DATA 2 VALID
P4 P3 P2 P1 P0 P7 P4 P3 P2 P1 P0P6
P5
0
t
v(Q)
DATA 1 VALID
P5 output voltage
I
trt(pu)
I
OH
P5 pull-up output current
t
rst(INT)
INT