The SYS module collects all user NMI （UNMI） sources， system NMI （SNMI） sources， and BOR/POR/PUC

　　sources of all the other modules. They are combined into three interrupt vectors. The interrupt vector

　　registers SYSRSTIV， SYSSNIV， SYSUNIV are used to determine which flags requested an interrupt or a

　　BOR/POR/PUC reset. The interrupt with the highest priority of a group， when enabled， generates a

　　number in the corresponding SYSRSTIV， SYSSNIV， SYSUNIV register. This number can be directly

　　added to the program counter， causing a branch to the appropriate portion of the interrupt service routine.

　　Disabled interrupts do not affect the SYSRSTIV， SYSSNIV， SYSUNIV values. A read access， read to the

　　SYSRSTIV， SYSSNIV， SYSUNIV register automatically resets the highest pending interrupt flag of that

　　register. If another interrupt flag is set， another interrupt is immediately generated after servicing the initial

　　interrupt. A write access to the SYSRSTIV， SYSSNIV， SYSUNIV register automatically resets all pending

　　interrupt flags of the group.