Abstract : Using a "general-purpose I/O card + dedicated computer software" to control stepper motors is not only economical but also offers excellent flexibility and stability. This paper introduces how to construct a CNC system using the Advantech PCL-731 digital input/output control card. The paper focuses on the control of pulse interval in such software CNC systems and the calculation methods and techniques for port pulse transmission. An application example is presented at the end. Keywords : CNC, I/O control card, software, robot, computer application 1 Introduction In the past, stepper motor control mainly used microcontroller systems because they were relatively inexpensive and technologically mature. However, microcontroller hardware systems are highly specialized, lack flexibility, and are difficult to program, making it challenging to create complex control systems. Furthermore, ordinary microcontroller systems can generally only control a small number of stepper motors, which is insufficient for controlling complex systems. With the increasing popularity of personal computers, the practice of directly controlling stepper motors with a PC has become increasingly popular, leading to the development of many dedicated PC cards for stepper motor control. However, these dedicated cards are expensive and can only control a limited number of motors. Currently, there are many general-purpose digital I/O cards on the market, reasonably priced, and offering a large number of output channels or bits. Therefore, using a "general-purpose I/O card + dedicated computer software" approach to control stepper motors is not only economical but also offers excellent flexibility and a user-friendly software interface. When necessary, a single computer can directly control dozens of stepper motors simultaneously, or leverage its network capabilities for complex engineering system control. Therefore, the "general-purpose I/O card + dedicated computer software" approach is an ideal stepper motor control system with significant potential for widespread adoption. Below, using the Advantech PCL-731 digital I/O card as an example, we will explain the system's composition and characteristics. 2 System Composition This system is based on a hardware platform, supplemented by appropriate software to implement control functions. The system's performance depends not only significantly on the hardware components but also closely on the quality of the developed control software. [b][align=center]For more details, please click: Using Digital I/O Cards to Control Stepper Motors[/align][/b]