Hi Sirs,
From TCA9539, We had link several interrupt input to different device
But only one INT connect to motherboard, our question is
1. The motherboard how to know which device send interrupt?
2. The motherboard is possible to check input Port value is same as original or not? or had others register can use?
Schematic:
Hey Shu-Cheng,
1. The motherboard how to know which device send interrupt?
-The TCA9539 will pull INT pin low when an input pin has changed values. In order to know which input has changed, you will need to have read the previous input values and store them on the master's memory. Then when the INT pin is pulled low, read the input registers and compare the previously stored values to the current values to find out which pin has changed states. You can compare by doing an XOR on previous vs. present.... whatever returns a 1 will be the one that has changed.
2. The motherboard is possible to check input Port value is same as original or not? or had others register can use?
There is no register in the TCA9539 which stores which pin has changed so unfortunately, you will have to use the process described in the first question-answer.
Lastly, the X value is determined by what ever you set the input values to externally. So if port1 had a pull up resistor tied to it, it would be a default 1.
Your schematic does not seem to have pull up or pull downs, which may result in the inputs fluctuating. It would be best if you put a pull up or pull down resistor to the inputs to make sure the input ports aren't floating and you will also know what the default starting values would be.I would recommend this for some of your points like, T1005 and T1004.
Extra: Your SDA/SCL buses will also need to have pull up resistors tied to them, I would recommend you tie them to the same Vcc as the TCA9539.
-Bobby
