4.3 Interrupt Operation
There are two interrupt sources in the VXC cards. They are named as INT0
and INT1. Their signal sources are as follows:
INT0: UART 0 interrupt output
INT1: UART 1 interrupt output
If only one interrupt signal source is used, the interrupt service routine doesn’t
need to identify the interrupt source.
If there is more than one interrupt source, the interrupt service routine needs
to identify the active signals by:
1. Reading the new status of all interrupt signal sources
2. Servicing it if INT0 is active
3. Servicing it if INT1 is active
Note:
If the interrupt signal is too short, the interrupt service routine cannot
identify which interrupt source is active. Therefore, the interrupt signal
must be in the hold_active state long enough for the interrupt service
routine to be executed. The hold_time is different for different Operating
Systems. The hold_time can be as short as a microsecond or as long as a
whole second. In general, 20mS is a long enough to for successful
execution under any OS.
VXC Cards User’s Manual (Ver. 1.1, 06/09.2005, pmh-012-01) -----38
