PCA9501 datasheet(8/22 Pages) PHILIPS

8 / 22 page

Philips Semiconductors

Product data

PCA9501

8-bit I2C and SMBus I/O port with interrupt,

2-kbit EEPROM and 6 address pins

2003 Sep 12

Interrupt (see Figs 9 and 12)

The PCA9501 provides an open drain output (INT) which can be fed

to a corresponding input of the microcontroller. This gives these

chips a type of master function which can initiate an action

elsewhere in the system.

An interrupt is generated by any rising or falling edge of the port

inputs in the input mode. After time tiv the signal INT is valid.

Resetting and reactivating the interrupt circuit is achieved when data

on the port is changed to the original setting or data is read from or

written to the port which has generated the interrupt.

Resetting occurs as follows:

• In the READ mode at the acknowledge bit after the rising edge of

the SCL signal

• In the WRITE mode at the acknowledge bit after the

HIGH-to-LOW transition of the SCL signal

• Returning of the port data to its original setting.

• Interrupts which occur during the acknowledge clock pulse may

be lost (or very short) due to the resetting of the interrupt during

this pulse.

Each change of the I/Os after resetting will be detected and, after

the next rising clock edge, will be transmitted as INT. Reading from

or writing to another device does not affect the interrupt circuit.

SW00790

PCA9501

(1)

INT

PCA9501

(2)

INT

PCA9501

(16)

INT

MICROCONTROLLER

INT

VDD

Figure 9. Application of multiple PCA9501s with interrupt

SDA

SCL

678

t ir

SW00791

ACKNOWLEDGE

FROM SLAVE

R/W

START CONDITION

STOP CONDITION

SLAVE ADDRESS (I/O EXPANDER)

DATA FROM PORT

DATA INTO I/O5

INT

I/O5

t iv

Figure 10. Interrupt generated by a change of input to I/O5

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