Chapter 2 Devices 2.2.6 Auxiliary Relays (M) The auxiliary relay has contact A and contact B. It can be used several times in the program. You can combine the control loops by using the auxiliary relay, but you cannot drive the external load using the auxiliary relay. You can use the auxiliary relays in either of the following two ways. 1. For general use: In general use, if an electric power failure occurs when the PLC is running, the auxiliary relay resets to the OFF state. When the power is restored, the auxiliary 2_ relay remains in the OFF state. 2. For latched use: In latched use, ff an electric power failure occurs when the PLC is running, the state of the auxiliary relay is retained.
When the power is restored, the relay state remains the same as before the power failure. 2.2.7 Special Auxiliary Relays (SM) Every special auxiliary relay has its specific function. Do not use the special auxiliary relays which are not defined. The special auxiliary relays and their functions are listed as follows. As to the SM numbers marked “*”, users can refer to the additional remarks on special auxiliary relays/special data registers. “R” in the attribute column indicates that the special auxiliary relay can read the data, whereas “R/W” in the attribute column indicates that it can read and write the data.
In addition, the mark “–” indicates that the status of the special auxiliary relay does not make any change. The mark “#” indicates that the system will be set according to the status of the PLC, and users can read the setting value and refer to the related manual for more information. 2-11 Latched Attribute Default OFF STOP RUN SM Function ON RUN STOP SM0 Error: the operation or operand exceeds the allowed range OFF OFF – N R OFF SM1 Error: the operation or operand exceeds the allowed range is locked.
OFF OFF – N R OFF SM5 Instruction inspection error OFF OFF – N R OFF SM6 Data lost in the latched area OFF – – N R/W OFF SM7 Insufficient power supply (24 V) OFF – – N R OFF *SM8 Watchdog timer error OFF – – N R OFF SM9 System error OFF – – N R OFF SM10 I/O bus error OFF – – N R OFF *SM22 Clearing the error log OFF OFF OFF N R/W OFF SM23 Clearing the download log OFF OFF OFF N R/W OFF SM24 Clearing the state-changing log of the PLC OFF OFF OFF N R/W OFF SM25 The online-editing processing flag is on when the online-editing mode starts. OFF – – N R OFF SM26 The debugging mode processing flag is on when the debugging mode starts. OFF – – N R OFF SM28 Error:
the output point is the same as the output that the high speed instruction used OFF OFF OFF N R/W OFF SM30 Error in the remote module OFF – – N R OFF