The input pins of the input capture module can be used as additional external interrupt sources if the input capture module is configured for operation in the external signal interrupt mode. This accomplished when the configuration bits ICM<2:0> are set to 111. Then, the input pins ICx on rising edge generate an interrupt request ICxIF. If the interrupt enable bit ICxIE is set and the interrupt priority level ICxIP<2:0>is defined, the microcontroller enters an interrupt.
NOTE: Inorder that the input capture module configured to operate in the external signal interrupt mode could operate in this mode, it is necssary to clear the control bits ICI<1:0> (ICxCON<6:5>= 0). Then, the interrupt is generated independently of the reading of the FIFO buffer. Also, the status bit ICOV has to be cleared.
The input capture module is very often used by the UART module for autodetection of the baud rate. In the autobaud mode the UART module is configured as follows: the control bit ABAUD (UxMODE<5>) is set i.e. the UART RX pin is internally connected to the input capture module input. and the ICx pin is disconnected from the rest of the input capture module.The baud rate is measured by measuring the the width of the START bit when a NULL character is received. Care should be taken that the input capture module is configured for the edge detection mode. For each microcontroller of the family dsPIC30F the input capture module assignment for each UART has been defined.