Receive Interrupts

Immediately after all data bits and the Stop bit have been received, the character in the RSR is transferred to the UART receive FIFO. The UxRXIF Interrupt flag in the respective PIR register is set at this time, provided it is not being suppressed.

The UxRXIF is suppressed by any of the following:

When the UART uses DMA for reception, suppressing the UxRXIF suspends the DMA transfer of data until software processes the error and reads UxRXB to advance the FIFO beyond the error.

The UxRXIF interrupts are enabled by setting all of the following bits:

The UxRXIF Interrupt Flag bit will be set when it is not suppressed and there is an unread character in the FIFO, regardless of the state of interrupt enable bits. Reading the UxRXB register will transfer the top character out of the FIFO and reduce the FIFO contents by one. The UxRXIF Interrupt Flag bit is read-only and therefore cannot be set or cleared by software.