运算符：__TRY、__CATCH、__FINALLY、__ENDTRY
这些运算符是从 IEC 61131-3 标准扩展而来的，它们用于 IEC 代码中的特定异常处理。
句法
__TRY
<statements_try>
__CATCH(exec)
<statements_catch>
__FINALLY
<statements_finally>
__ENDTRY
<statements_next>当声明中的 __Try 运算符抛出异常，应用程序不会停止。相反，它执行下面的语句 __Catch 因此开始异常处理。然后它执行下面的指令 __FINALLY .异常处理以 __ENDTRY.然后应用程序执行下一条语句。
异常的 IEC 变量具有数据类型 __System.ExceptionCode.
例 152. 例子
如果声明在 __TRY 抛出异常，则程序执行不会停止。相反，中的声明 __CATCH 被执行。因此，在本例中 exc 函数被执行，然后下面的语句 __FINALLY.然后它执行下面的指令 __FINALLY.
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 instruction is tested. If it produces an exception, the statement under __CATCH is executed first and then the statement under __FINALLY.
__CATCH(exc)
HandleException(exc, strExceptionText => strExceptionText);
__FINALLY
GVL.g_count := GVL.g_count + 2;
__ENDTRY有关更多信息，请参阅： 在处理的异常处停止执行
数据类型“__System.ExceptionCode”
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