TCA9539-Q1: TCA9539-Q1：Interrupt behavior

Qin Heater

Part Number: TCA9539-Q1
Other Parts Discussed in Thread: TCA9539

Tool/software:

Hi，team：

For the TCA9539, I have two questions I'd like to inquire about:

1、Under what circumstances would the INT (interrupt) remain consistently low? Have you encountered such a scenario? what If I flip the voltage state of a certain port and maintain it, and do not read the device through I2C, will the INT remain consistently low?

2、If the voltage level has already flipped on a certain port and triggered an interrupt, causing the INT to stay low, what would happen if another port's voltage level flips afterwards? In this case, if second port returns to its normal state and first port remain INT state， would the INT go back to high, or would it remain low?

Best regards,

Heater

9 months ago

0 Clemens Ladisch 9 months ago

Guru 317370 points

The /INT output is low when for any pin, the current state is different from the state when the input register was last read.

1. The /INT pin remains low when you do not read the input register of a changed pin.

2. /INT remains low as long as any pin is in a changed state.

0 Qin Heater 9 months ago in reply to Clemens Ladisch

Prodigy 70 points

So, for both of my two questions, The INT pin always remains low?

0 Tyler Townsend 9 months ago in reply to Qin Heater

TI__Mastermind 48308 points

Hi Heater,

In both cases, the interrupt will stay low.

In respond to your second question, if the interrupt is being triggers by two IO's on two separate ports, both input ports must be read before the interrupt will release on /INT.

Regards,

Heater

0 Qin Heater 8 months ago in reply to Tyler Townsend

Prodigy 70 points

Another qustion:

If one pin changed from H to L and remained the state until controller read 9539 and INT released；then that pin's normal state still H or changed to L？ and now will INT assert to L if the pin from L to H ？

0 Clemens Ladisch 8 months ago in reply to Qin Heater

Guru 317370 points

Yes; reading the input register changes the 'normal' state.

0 Tyler Townsend 8 months ago in reply to Clemens Ladisch

TI__Mastermind 48308 points

Hi Qin,

Please let me know if you have additional questions.

Regards,

Tyler

0 Qin Heater 8 months ago in reply to Tyler Townsend

Prodigy 70 points

The last qustion:

How do you understand this sentence?

If If port is set to input from output mode then INT will be asserted？

and if port is set to output, changed to default mode(input) because of reset asserting，the INT will be asserted or not?

Best regards,

Heater

+1 Tyler Townsend 8 months ago in reply to Qin Heater

TI__Mastermind 48308 points

Heater,

Say the original state of your input is HIGH (logic 1).

If that pin is changed to an output, the output will continue to operate without causing an interrupt on /INT.

If you change that pin from an output to and input, and the input logic state some how becomes a LOW (logic 0), then the interrupt will trigger because the input is different from its original state.

Qin Heater said:
and if port is set to output, changed to default mode(input) because of reset asserting，the INT will be asserted or not?

/INT will not be asserted when resetting the Pxx pins to their default state.

Regards,

Tyler

0 Qin Heater 8 months ago in reply to Tyler Townsend

Prodigy 70 points

Thanks for your answers!

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TCA9539-Q1: TCA9539-Q1：Interrupt behavior