Abstract: In order to meet the requirements of real-time and stability in the process of signal acquisition and transmission in the machining of CNC, such as the hardware limit signal of axis movement, gas signal,water signal, tool measurement signal and others, and to establish communication with programmable controllers for data exchange to detect and control digital signal. This article designs and develops a digital module with the EtherCAT communication protocol which is based on Ethernet technology. The software and hardware design of the digital module and the execution process of the data interaction program is studied. Experiments are conducted in conjunction with the standard EtherCAT communication master station TwinCAT to demonstrate that the developed digital module can establish communication and transmit data with the master station normally, and maintain synchronization with the communication cycles in EtherCAT bus.A tool measurement scheme for machine tools was designed based on digital signal detection in machine tool processing. The results showed that the calculation of tool wear errprs based on the real-time response to measurement input signal by the digital module met the requirements of machine tool processing. The digital module has practical engineering value and achieves the research purpose.