PCA9671 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2011. All rights reserved.
Product data sheet Rev. 3 — 29 September 2011 13 of 33
NXP Semiconductors
PCA9671
Remote 16-bit I/O expander for Fm+ I
2
C-bus with reset
8.3 Reading from a port (Input mode)
All ports programmed as input should be set to logic 1. To read, the master
(microcontroller) first addresses the slave device after it receives the interrupt. By setting
the last bit of the byte containing the slave address to logic 1 the Read mode is entered.
The data bytes that follow on the SDA are the values on the ports.
If the data on the input port changes faster than the master can read, this data may be
lost.
Fig 14. Write mode (output)
A5 A4 A3 A2 A1 A0 0 ASA6
slave address
START condition R/W
acknowledge
from slave
002aac250
P
06
1
P
07
data to port 0
A
acknowledge
from slave
12345678SCL 9
SDA
A
acknowledge
from slave
write to port
data output from port
t
v(Q)
P05
data to port 1
data A0 and B0 valid
P16 output voltage
I
trt(pu)
I
OH
P16 pull-up output current
P
04
P
03
P
02
P
01
P
00
P
17
P
14
P
13
P
12
P
11
P
10
1
P16
P
15
t
v(Q)
DATA A0 AND B0 VALID
P05 output voltage
I
trt(pu)
I
OH
P05 pull-up output current
