Product Description:

The EL1252 digital input terminal is produced by Beckhoff within the EL EtherCAT Terminals series. As a two-channel input module, it captures fast binary sensor signals and attaches precise timestamps to those transitions for synchronized machine control. By connecting to the distributed clock domain of an EtherCAT network, the terminal feeds edge-accurate status information to the PLC. This timing data allows motion axes, counters, and control logic to react deterministically to input changes.

Each input channel works with a 64-bit internal clock that rolls over from the epoch 2000-01-01 00:00. Clock increments occur in 1 ns steps, so every captured edge is registered with nanosecond granularity. The module provides two digital inputs, allowing its timing logic to focus on those individual signal lines. Distributed clock precision remains less than 1 µs across the network. Whenever a state change occurs, the terminal forwards an event payload containing the current 0/1 state and timestamp field pair to the master. This event-driven operation avoids fixed-rate polling and reduces unnecessary bus traffic when the input states remain unchanged.

For applications that must distinguish multiple transitions within one EtherCAT cycle, the terminal can record the first or last edge detected during that period. This selection works with the event-based sampling mode, which begins timestamping when input activity is present. The internal buffer retains one rising and one falling edge per cycle, allowing the controller to receive both transition directions at high input frequencies. The captured timing data can support deterministic counting, cam control, and latch functions without external latch circuitry or separate high-speed counter cards. These capabilities are useful when sensor transitions must be correlated with motion events or other distributed signals on the EtherCAT network.