MCP23016-ISLASHML datasheet(12/38 Pages) MICROCHIP

12 / 38 page

MCP23016

DS20090C-page 12

1.8

Serializer/Deserializer

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.

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.

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.

1.9.1

INTERRUPT EVENT DETECTION

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.

FIGURE 1-2:

READING PORTX AFTER

INTERRUPT EVENT

Port value

PORT X

GPx

INT

is captured

and written to

INTCAPn

Port value

is captured

and written to

INTCAPn

Read GPx

or INTCAPn

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