Datasheet

PCA9575 All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 4 — 20 May 2014 19 of 42
NXP Semiconductors
PCA9575
16-bit I
2
C-bus and SMBus, level translating, low voltage GPIO
7.9 Software reset
The Software Reset Call allows all the devices in the I
2
C-bus to be reset to the power-up
state value through a specific formatted I
2
C-bus command. To be performed correctly, it
implies that the I
2
C-bus is functional and that there is no device hanging the bus.
The Software Reset sequence is defined as following:
1. A START command is sent by the I
2
C-bus master.
2. The reserved General Call I
2
C-bus address ‘0000 000’ with the R/W bit set to 0 (write)
is sent by the I
2
C-bus master.
3. The PCA9575 device(s) acknowledge(s) after seeing the General Call address
‘0000 0000’ (00h) only. If the R/W
bit is set to logic 1 (read), no acknowledge is
returned to the I
2
C-bus master.
4. Once the General Call address has been sent and acknowledged, the master sends
1 byte. The value of the byte must be equal to 06h (1000 0011).The PCA9575
acknowledges this value only. If the byte is not equal to 06h, the PCA9575 does not
acknowledge it. If more than 1 byte of data is sent, the PCA9575 does not
acknowledge anymore.
5. Once the right byte has been sent and correctly acknowledged, the master sends a
STOP command to end the Software Reset sequence: the PCA9575 then resets to
the default value (power-up value) and is ready to be addressed again within the
specified bus free time. If the master sends a Repeated START instead, no reset is
performed. The I
2
C-bus master must interpret a non-acknowledge from the PCA9575
(at any time) as a ‘Software Reset Abort’. The PCA9575 does not initiate a software
reset.
7.10 Interrupt output (INT)
The open-drain active LOW interrupt is activated when one of the port pins changes state
and the port pin is configured as an input and the interrupt on it is not masked. The
interrupt is deactivated when the port pin input returns to its previous state or the Input
Port register is read. It is highly recommended to program the MSK register, and the CFG
registers during the initialization sequence after power-up, since any change to them
during Normal mode operation may cause undesirable interrupt events to happen.
Remark: Changing an I/O from an output to an input may cause a false interrupt to occur
if the state of the pin does not match the contents of the Input Port register. Only a Read of
the Input Port register that contains the bit(s) image of the input(s) that generated the
interrupt clears the interrupt condition.
7.11 Standby
The PCA9575 goes into standby when the I
2
C-bus is idle. Standby supply current is lower
than 2.0 A (typical).