Obviously every instruction is in a PLC for a reason, and there are situations in which using them is needed.
But I cannot stand it when people use the MCR (Master Control Reset) instruction in a SLC/Logix program. I understand their use and how powerful they are, but I've found they trip me up more often than not. Especially when you have multiple MCR sections in a ladder file. I'd rather use a rung with all of my "Okay to run" conditions in series, and then use that internal register to enable each individual output rung. It's not that big of a deal, but it can cost you a few minutes if you're trying to figure out why the OTx instruction isn't lighting up even though the rung is true and it's not a double coil.
But I cannot stand it when people use the MCR (Master Control Reset) instruction in a SLC/Logix program. I understand their use and how powerful they are, but I've found they trip me up more often than not. Especially when you have multiple MCR sections in a ladder file. I'd rather use a rung with all of my "Okay to run" conditions in series, and then use that internal register to enable each individual output rung. It's not that big of a deal, but it can cost you a few minutes if you're trying to figure out why the OTx instruction isn't lighting up even though the rung is true and it's not a double coil.