PROGRAM Startup
VAR
RetValReadIO : EnumSetAndGetSafeValue;
RetValIO : BOOL;
END_VAR

REPEAT
//get safe value for waiting for the communication
RetValReadIO := _getSafeValue( Variable := i_start_get_256,
accessmode := default_value,
getvalue := RetValIO);

UNTIL (RetValReadIO = OK)
END_REPEAT;

myRetDINT :=_waittime(t#3s);
g_boFirstRun := 1;

END_PROGRAM

在SIMOTION起动时加载到STARTUP任务中，要读取IW256的返回值，这个IW256有可能是与什么相关的变量呢？