pca9670 NXP Semiconductors, pca9670 Datasheet - Page 11

• Manufacturer Part Number: pca9670
• Description: Pca9670 Remote 8-bit I/o Expander For Fm I?c-bus With Reset
• Manufacturer: NXP Semiconductors

NXP Semiconductors
8. I/O programming
PCA9670_2
Product data sheet
Fig 12. Write mode (output)
SDA
SCL
data output from port
P5 output voltage
P5 pull-up output current
write to port
S A6
START condition
1
A5 A4 A3 A2 A1 A0 0
2
8.1 Quasi-bidirectional I/O architecture
8.2 Writing to the port (Output mode)
slave address
3
4
The PCA9670’s 8 ports (see
input or output ports. Input data is transferred from the ports to the microcontroller in the
Read mode (see
Figure
This quasi-bidirectional I/O can be used as an input or output without the use of a control
signal for data directions. At power-on the I/Os are HIGH. In this mode only a current
source (I
edges into heavily loaded outputs. These devices turn on when an output is written HIGH,
and are switched off by the negative edge of SCL. The I/Os should be HIGH before being
used as inputs. After power-on, as all the I/Os are set HIGH, all of them can be used as
inputs. Any change in setting of the I/Os as either inputs or outputs can be done with the
write mode.
Remark: If a HIGH is applied to an I/O which has been written earlier to LOW, a large
current (I
To write, the master (microcontroller) first addresses the slave device. By setting the last
bit of the byte containing the slave address to logic 0 the write mode is entered. The
PCA9670 acknowledges and the master sends the data byte for P7 to P0 and is
acknowledged by the PCA9670. The 8-bit data is presented on the port lines after it has
been acknowledged by the PCA9670.
The number of data bytes that can be sent successively is not limited. The previous data
is overwritten every time a data byte has been sent.
5
6
12).
7
OH
OL
R/W
8
) to V
) will flow to V
9
A
acknowledge
from slave
DD
P7
Figure
P6 1
is active. An additional strong pull-up to V
P5
Rev. 02 — 17 July 2007
13). Output data is transmitted to the ports in the Write mode (see
SS
P4 P3 P2 P1 P0
data 1
.
Figure
Remote 8-bit I/O expander for Fm+ I
I
trt(pu)
2) are entirely independent and can be used either as
A
acknowledge
from slave
P7
t
v(Q)
I
0
P5
OH
P5
DATA 1 VALID
P4 P3 P2 P1 P0
data 2
DD
(I
trt(pu)
A
acknowledge
from slave
PCA9670
) allows fast rising
DATA 2 VALID
t
© NXP B.V. 2007. All rights reserved.
2
v(Q)
C-bus with reset
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