SCPS128D July 2006 – March 2021 PCA9554
The INT will be improperly de-asserted if the following two conditions occur:
This generally means the last operation with the device was a Read of the input register. However, the command byte may have been written with 00h without ever going on to read the input register. After reading from the device, if no other command byte written, it will remain 00h.