Commonly, setting K17.1 = 1 enables the I/O softkey to output PMC parameters like K relays, counters, and timers to a memory card or via RS-232.
Note: Exact exclusive Keep Relay addresses vary by FANUC controller series and PMC model (Ladder I, II, III, etc.). Always verify against the specific controller’s manual set.
While Keep Relays hold data without power, they are often excluded from standard SRAM backups unless specifically configured. When cloning a machine, failure to clear or set the correct Keep Relays can lead to configuration mismatches. fanuc keep relay parameters exclusive
A common requirement in machine tool automation is creating "exclusive" logic using these keep relays. This article covers how to configure, modify, and utilize FANUC keep relay parameters when you need mutually exclusive operations. What are FANUC Keep Relays?
Only modify Keep Relays if you have the exclusive documentation from the machine builder. Changing the wrong bit can disable emergency stop circuits or cause physical damage. Commonly, setting K17
Some Keep Relays are exclusively "write-once" or "latching." For example, a Keep Relay that enables a paid option (like high-speed machining) may be set to 1 by an OEM field engineer and then permanently locked. Even if you try to change it back to 0 , the ladder logic will ignore the change due to a memory-protect key or a secondary hardware dongle.
If a change to a system relay doesn't take effect immediately, cycling the emergency stop or powering down the machine may be necessary. While Keep Relays hold data without power, they
(often labeled PMC or PMCMNT ) repeatedly until you see PMCLAD .
Unlike standard data parameters, , meaning they retain their settings (0 or 1) even after the power is turned off. They act as the bridge between machine operator settings and the internal PMC (Programmable Machine Controller) logic. 1. What Are FANUC Keep Relays (K-Parameters)?
The machine stops mid-cycle without generating a standard FANUC system alarm. The PMC ladder is waiting for an input condition that can never be fulfilled because two opposing Keep Relays are fighting for control over the same internal coil ( R address). Interlock Defeats and Safety Violations