COMMUNICATION SAFETY SYSTEM FOR DATA HIGHWAY

摘要

The method concerns that the master data acquisition computer supervising the slave programmable controller does not change the status of registers which may cause the hazardous situations. The memory part of the programmable controller is allocated as the buffer area accessing to the slave process control computer and the data acquisition computer. During scanning each process control computer, the status of input and output registers are changed and the selected status is shifted from the buffer to corresponding area. The data acquisition computer only accesses to the information in the buffer of each process control computer.