Abstract: VMEbus interface system is the hardware channel which connects a PLC coprocessor board with a host machine. It should undertake the communication of the PLCboard, and cater to the various protocols which the bus and operating system of the hostmachine require on hardware and software. This paper compares the data transfer byusing the PLC board as the bus master device with DMA and the bus slave device without DMA under the circumstance of SUN OS and VMEbus. We tested the data transferrate, adopted the reasonable method, and implemented the VMEbus interface betweenthe PLC board and SUN3/SUN4 workstation by FPGA （Field Programmable Gate Array）.