C.7 Communications Timing C.7 Communications Timing To prevent overrun in the slave drive, the master should wait a certain time between sending messages to the same drive. In the same way, the slave drive must wait before sending response messages to prevent an overrun in the master. This section explains the message timing. u Command Messages from Master to Drive In order to prevent overrun and data loss, the master must wait between receiving a response and sending the same type of command as before to the same slave drive. The minimum wait time depends on the command as shown in the table below.
Table C.2 Minimum Wait Time for Sending Messages If the drive receives command type 1 data during the minimum wait time, it will perform the command and then respond. However, if it receives a command type 2 or 3 during that time, either a communication error will result or the command will be ignored. PLC→Drive PLC→Drive Drive→PLC 24 bit length Master Send Wait Time Figure C.7 Minimum Wait Time for Sending Messages A timer should be set in the master to check how long it takes for the slave drive(s) to respond to the master. If no response is received within a certain amount of time, the master should try resending the message.
u Response Messages from Drive to Master If the drive receives a command from the master, it will process the data received and wait for the time set in H5-06 until it responds. Increase H5-06 if the drive response causes overrun in the master.
PLC→Drive PLC→Drive Drive→PLC 24 bit length H5-06 setting Figure C.8 Minimum Response Wait Time 194 SIEP C710606 33A OYMC AC Drive – J1000 User Manual Command Type Example Minimum Wait Time 1 • Control command (Run, Stop) • Set inputs/outputs • Read monitors and parameter values 10 ms 2 • Write parameters 50 ms 3 • Save changes using an Enter command 3 to 5 s Command message Response message Command message Time Command message Response message Command message Time