The TXE8124 devices generate an interrupt on any rising or falling edge of an input I/O, provided that the interrupt for that I/O is not masked. When an input pin state is different than the input read register state, the corresponding interrupt flag bit is set, and the INT output is asserted. The INT pin is open-drain and requires an external pull-up resistor to V_CC use the interrupt feature, otherwise it may be left floating.

I/Os configured as outputs do not generate interrupts. Switching a pin from output to input may generate a fault interrupt if the actual pin level does not match the stored input port register value. If an I/O port was previsouly in input state and detected an interrupt as switching to output, this won't clear the interrupt flag. It only masks the interrupt pin. Then when the port is reconfigured as input, the interrupt comes back.

With the following conditions, the interrupt status bits can be cleared and the INT pin de-asserted.

• Hardware reset from RESET pin - this de-asserts the interrupt temporarily as POR is going to assert the interrupt
• Entering fail-safe mode - this disables and de-assert the interrupt
• Reading Interrupt Flag Status Register
• Setting the corresponding bit as 1 in Interrupt Mask Register

There are four sources of interrupts in TXE8124:

1. Smart Input Pin Interrupt: Smart Interrupt is enabled or disabled at I/O port level by setting the corresponding port bit in the Smart Interrupt Register. If Smart Interrupt (the corresponding register bit as 0) is enabled and an interrupt is generated, the interrupt clears if the I/O state goes back to the intial logic state or it reads the Interrupt Flag Status Register. For example, if the Input Port Register is read and/or the I/O state goes back to the initial state, the interrupt is cleared even if there is no reading operation on the Interrupt Flag Status Register. Refer to Table 7-1 for the different interrupt clearing scenarios. To avoid missing the interrupt clear due to false IO toggle, it is strongly recommended to enable the glitch filter enable in the Input Glitch Filter Enable Register.
2. Regular Input Pin Interrupt: When Smart Interrupt is disabled (the corresponding register bit as 1) in the Smart Interrupt Register, the I/O state going back to the initial logic state cannot clear the interrupt, only reading the Interrupt Flag Status Register clears the interrupt.
   Table 7-1 Interrupt Flag Clearing Scenarios for Smart Interrupt

   Smart Interrupt	CS state when IO input changes	Interrupt flag clears
   Disable	CS = High	CS to be low and SPI reading Interrupt Flag Status Register
   Disable	CS = Low	Reading Interrupt Flag Status Register
   Enable	CS = High	CS to be low and SPI reading Input Port Register IO state going back to the initial state CS to be low and SPI reading Interrupt Flag Status Register
   Enable	CS = Low	Reading Input Port Register or IO states going back to the initial state will not clear the interrupt flag immediately. After CS becomes high and holds over 30ns, the interrupt flag is cleared. Reading Interrupt Flag Status Register

3. POR Interrupt : the POR fault bit is set in the Fault Status Register for each POR recovery, which also generates an interrupt. The interrupt is only cleared when the Fault Status Register is read.
4. Fail-safe Redundancy Failure Interrupt: When the fail-safe redundancy check is enabled, and if any fail-safe redundancy check failure occurs, a fail-safe sync fault bit is set in the Fault Status Register. This also generates an interrupt. The interrupt is only cleared when the Fault Status Register is read.

Interrupt Masking

Interrupts from all input I/Os are unmasked by default. To mask an interrupt, the corresponding I/O bit needs to be set in the interrupt mask register. The interrupt generated by POR recovery cannot be masked.

If the state of an input I/O is changed and the corresponding bit in the Interrupt mask register is set to 1, the interrupt is masked and the INT pin is not asserted. The corresponding bit in the interrupt flag status register also stays at 0 and is blocked by the interrupt mask bit.

The interrupts generated by fail-safe redundancy check fail is disabled if the fail-safe redundancy check enable bit is 0.

Multiple ports can be configured for interrupt masking at the same time by using multi port command.