MCP23016
1.9.1
INTERRUPT EVENT DETECTION
1.8
Serializer/Deserializer
The IARES bit controls the resolution for detecting an
interrupt-on-change event. If this bit is ‘0’ (default), the
maximum time for detecting a change of event is high,
which results in lower standby current. If this bit is ‘1’, it
takes less time for scanning the activity on the port and
results in higher standby current.
The Serializer/Deserializer block converts and
transfers data between the I2C bus and GPIO.
1.9
Interrupt Logic
The MCP23016 asserts the open-drain interrupt output
(INT) low when one of the port pins changes state. Only
those pins that are configured as an input can cause an
interrupt. Pins defined as an output have no effect on
INT. The interrupt will remain active until a read from
either the port (GPn) on which the interrupt occurred or
the INTCAPn register is performed. If the input returns
to its previous state before a read operation, it will reset
the interrupt and the INT pin output will tri-state. Each
8-bit port is read separately, so reading GP0 or
INTCAP0 will not clear the interrupt generated by GP1
or INTCAP1, and vice versa.
FIGURE 1-2:
READING PORTX AFTER
INTERRUPT EVENT
PORT X
PORT X
GPx
INT
Input change activity on each port will generate an
interrupt and the value of the particular port will be
captured and copied into INTCAP0/INTCAP1. The
INTCAPn registers are only updated when an interrupt
occurs on INT. These values will stay unchanged until
the user clears the interrupt by reading the port or the
INTCAPn register.
Port value
is captured
and written to
INTCAPn
Port value
is captured
and written to
INTCAPn
Read GPx
or INTCAPn
If the input port value changes back to normal before a
user-read, the INT output will be reset. However, the
INTCAP0/INTCAP1 will still contain the value of the
port at the interrupt change. If the port value changes
again, it will re-activate the interrupt and the new value
will be captured.
The first interrupt on change event following an
interrupt RESET will result in a capture event. Any fur-
ther change event that occurs before the interrupt is
reset will not result in a capture event.
DS20090C-page 12
© 2007 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
