Hardware Design of the Main Control System for CNC Machines

Hardware Design of the Main Control System for CNC Machines

Unlike the conventional main control method using ARM + FPGA, this solution employs a single CMC chip as the control core, effectively reducing the complexity of the main control circuit.

This solution uses the CMC693PR144 chip for circuit design. The chip has a maximum main frequency of 200MHz and includes 2 UART serial ports, 2 SPI interfaces, 2 CAN interfaces, 2 Ethernet interfaces, and 1 I2C interface. For RS232 and RS485 interface expansion, MAX3232 and SN65176 chips are used respectively, with signal isolation implemented. An external network PHY chip, DP83848, is used to achieve 100Mbps Ethernet. To meet industrial environment requirements, the power supply uses an independent isolation power module, and the IO circuit is also isolated, with an IO frequency of up to 10kHz.

To meet the differential pulse input requirements of most servo systems, a general chip for single-ended to differential conversion is needed. This system uses the AM26LS31 chip, which meets the 4MHz output frequency requirement. Additionally, the circuit supports differential signal input, such as quadrature encoder differential signals, through the AM26LS32 chip, with a maximum input frequency of up to 10MHz.

The system can also expand high-precision ADC and DAC through the I2C interface, including 0-10V voltage input/output and 4-20mA current input/output, with a resolution of up to 16 bits. Additionally, the system features power-down detection and power-down storage circuits, allowing timely saving of critical data in case of sudden power loss. The physical diagram of the entire circuit is shown in Figure 3. From the complexity of the physical circuit, it is evident that the overall hardware design workload can be significantly simplified. Compared to a motion controller with the same functionality, the number of components can be reduced by 26%, the number of solder joints by 31%, and the code volume by 91%, resulting in a corresponding 91% reduction in manpower investment.