modbus communication between acs355 vfd and pm554 via frsa card
In my application three acs355 drives are controlled using ac500 eco plc pm554 with com2 of plc through frsa card fitted in acs355 drives. The drive communicates perfectly with the master plc through modbus protocol .while testing i found one of the drive (randomly) goes to stop mode still in the presence of the the start bit= TRUE .im using ACS3XX_COM_MOD_RTU,ACS_DRIVES_CTRL_STANDARD fb's .i ve assigned a vfd_pgm to run cyclic which calls the 3 drives contol pgm's for a period of 60ms . please suggest remedy for this problem.
I can suggest to check if in other position of the program, the start bit of the drive could be change from TRUE to FALSE, depending of the elaboration of the program of the POU.....it can happen due to a different processing of the machine cycle.
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