B.6 Communications TimingTo prevent a communications overrun in the slave drive, the master should wait a certain time between sending messages tothe same drive. In the same way, the slave drive must wait before sending response messages to prevent an overrun in themaster. This section explains the message timing.u Command Messages from Master to DriveThe master must wait for a specified time between receiving a response and resending the same type of command to the sameslave drive to prevent overrun and data loss. The minimum wait time depends on the command as shown in the table below.Table B.2 Minimum Wait Time for Sending MessagesCommand Type Example Minimum Wait Time1• Control command (Run, Stop)• Set inputs/outputs• Read monitors and parameter values5 ms2 • Write parameters 50 ms3 • Save changes using an Enter command 3 to 5 s <1><1> If the drive receives command type 1 data during the minimum wait time, it will perform the command and then respond. However, if it receivesa command type 2 or 3 during that time, either a communication error will result or the command will be ignored.Command message Response message Command messagePLC→Drive PLC→DriveDrive→PLC24 bit length Master SendWait TimeTimeFigure B.7 Minimum Wait Time for Sending Messagesu Response Messages from Drive to MasterIf the drive receives a command from the master, it will process the data received and wait for the time set in H5-06 until itresponds. Increase H5-06 if the drive response causes overrun in the master.TimeCommand message Response message Command messagePLC→Drive PLC→DriveDrive→PLC24 bit length H5-06settingFigure B.8 Minimum Response Wait TimeB.6 Communications TimingYASKAWA ELECTRIC SIEP YEAHHP 01B YASKAWA AC Drive – A1000 HHP Programming Manual 323B MEMOBUS/ModbusCommunications
