holding relays

[wdieckm 0]

Can someone help me to understand the Keep/holding relays work? C20K program

[PMCR 66]

These are 2 seperate items. KEEP is a function Holding Relays are bits in the Holding Relay memory area. First, the KEEP. Keep is basically a latch, or a dual coil latching relay. It is a function with 2 inputs, SET and RESET. When the SET input is turned on, the bit inside the KEEP function is turned on. When the RESET input is turned on, the bit inside the KEEP function is turned off. If the SET and RESET inputs are both turned on, the RESET input wins. You can review any Omron manual for this instruction. It has remained basically the same since the first use. Now for the Holding Relays. HR bits are bits located in the Holding Relay memory area. The unique feature of this memory area is the the values in the HR memory area are maintained (by the battery) when power is cycled to the PLC.

[BobB 58]

Just be careful when using KEEP function - if you miss something in the program that you should use to reset the KEEP you can be in big trouble - extreme care needed when programming this function.