这些运算符由 IEC 61131-3 标准扩展而来，用于 IEC 代码中的特定异常处理。
语法
__TRY <statements_try> __CATCH(exec) <statements_catch> __FINALLY <statements_finally> __ENDTRY <statements_next>
当__Try 操作符中的语句抛出异常时，应用程序不会停止运行。相反，应用程序会执行__Catch 中的语句，启动异常处理，然后执行__FINALLY 中的语句。异常处理以__ENDTRY 结束，应用程序执行后续语句。
异常的 IEC 变量数据类型为__System.ExceptionCode 。
示例
如果__TRY 中的语句抛出异常，则程序执行不会停止。取而代之的是执行 __CATCH 中的语句。因此，在本例中，应用程序先执行exc 函数，然后执行__FINALLY 中的语句，最后执行__ENDTRY 中的语句。
FUNCTION Tester : UDINT VAR_INPUT count : UDINT; END_VAR VAR_OUTPUT strExceptionText : STRING; END_VAR VAR exc : __SYSTEM.ExceptionCode; END_VAR __TRY Tester := tryFun(count := count, testcase := g_testcase); // This statement is tested. If it throws an exception, then the statement in __CATCH is executed first, and then the statement in __FINALLY. __CATCH(exc) HandleException(exc, strExceptionText => strExceptionText); __FINALLY GVL.g_count := GVL.g_count + 2; __ENDTRY
数据类型 "__系统.异常代码
TYPE ExceptionCode : ( RTSEXCPT_UNKNOWN := 16#FFFFFFFF, RTSEXCPT_NOEXCEPTION := 16#00000000, RTSEXCPT_WATCHDOG := 16#00000010, RTSEXCPT_HARDWAREWATCHDOG := 16#00000011, RTSEXCPT_IO_CONFIG_ERROR := 16#00000012, RTSEXCPT_PROGRAMCHECKSUM := 16#00000013, RTSEXCPT_FIELDBUS_ERROR := 16#00000014, RTSEXCPT_IOUPDATE_ERROR := 16#00000015, RTSEXCPT_CYCLE_TIME_EXCEED := 16#00000016, RTSEXCPT_ONLCHANGE_PROGRAM_EXCEEDED := 16#00000017, RTSEXCPT_UNRESOLVED_EXTREFS := 16#00000018, RTSEXCPT_DOWNLOAD_REJECTED := 16#00000019, RTSEXCPT_BOOTPROJECT_REJECTED_DUE_RETAIN_ERROR := 16#0000001A, RTSEXCPT_LOADBOOTPROJECT_FAILED := 16#0000001B, RTSEXCPT_OUT_OF_MEMORY := 16#0000001C, RTSEXCPT_RETAIN_MEMORY_ERROR := 16#0000001D, RTSEXCPT_BOOTPROJECT_CRASH := 16#0000001E, RTSEXCPT_BOOTPROJECTTARGETMISMATCH := 16#00000021, RTSEXCPT_SCHEDULEERROR := 16#00000022, RTSEXCPT_FILE_CHECKSUM_ERR := 16#00000023, RTSEXCPT_RETAIN_IDENTITY_MISMATCH := 16#00000024, RTSEXCPT_IEC_TASK_CONFIG_ERROR := 16#00000025, RTSEXCPT_APP_TARGET_MISMATCH := 16#00000026, RTSEXCPT_ILLEGAL_INSTRUCTION := 16#00000050, RTSEXCPT_ACCESS_VIOLATION := 16#00000051, RTSEXCPT_PRIV_INSTRUCTION := 16#00000052, RTSEXCPT_IN_PAGE_ERROR := 16#00000053, RTSEXCPT_STACK_OVERFLOW := 16#00000054, RTSEXCPT_INVALID_DISPOSITION := 16#00000055, RTSEXCPT_INVALID_HANDLE := 16#00000056, RTSEXCPT_GUARD_PAGE := 16#00000057, RTSEXCPT_DOUBLE_FAULT := 16#00000058, RTSEXCPT_INVALID_OPCODE := 16#00000059, RTSEXCPT_MISALIGNMENT := 16#00000100, RTSEXCPT_ARRAYBOUNDS := 16#00000101, RTSEXCPT_DIVIDEBYZERO := 16#00000102, RTSEXCPT_OVERFLOW := 16#00000103, RTSEXCPT_NONCONTINUABLE := 16#00000104, RTSEXCPT_PROCESSORLOAD_WATCHDOG := 16#00000105, RTSEXCPT_FPU_ERROR := 16#00000150, RTSEXCPT_FPU_DENORMAL_OPERAND := 16#00000151, RTSEXCPT_FPU_DIVIDEBYZERO := 16#00000152, RTSEXCPT_FPU_INEXACT_RESULT := 16#00000153, RTSEXCPT_FPU_INVALID_OPERATION := 16#00000154, RTSEXCPT_FPU_OVERFLOW := 16#00000155, RTSEXCPT_FPU_STACK_CHECK := 16#00000156, RTSEXCPT_FPU_UNDERFLOW := 16#00000157, RTSEXCPT_VENDOR_EXCEPTION_BASE := 16#00002000 RTSEXCPT_USER_EXCEPTION_BASE := 16#00010000 ) UDINT ; END_TYPE