PCA9545A: Interrupt function

Hi Jeong,

1. As I said yesterday, we don't have any I/O expanders currently that latch the INT pin when an input port changes value.

2. Yes, you can clear the interrupts individually. They will each individually show if they have an interrupt in the control register:

Best,

Chris

2. No, these four bits are read only. A bit clears only when the external interrupt signal goes high again.

That is correct. Maybe my response is a little misleading but these are input pins so this device has no way of clearing those interrupts since it is not generating them. I thought this was assumed in the question but I am seeing now how my response could have come off as confusing.

What I mean to say in my post is that you can use the register to see which interrupts are being generated. Then you will have to go to the device generating it and clear it yourself. I assume that is what they meant by clearing it one by one. The idea that you can see which specific interrupt is being generated.

Hopefully that makes more sense. If there are any other questions let me know.

Best,

Chris

Thank you for answer.

If so, can MCU read INT signal sent for 250us from 1 out of 4 slaves?

When one of the slaves actives the interrupt for 250 µs, then the /INT output of the PCA is active of 250 µs. If the MCU cannot react and read the control register in this time, then it has to check all slaves for which one generated the interrupt.

That is correct. Just a note the interrupt valid time (the time for an interrupt to propagate from input INTn pin to the output INT pin) is at max 4us:

In practice it will be much faster than 4 us.

Best,

Chris