D.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 BypassThe master must wait for a specified time between receiving a response and resending the same type of command to the samebypass drive to prevent overrun and data loss. The minimum wait time depends on the command as shown in Table D.1.Table D.1 Minimum Wait Time for Sending MessagesCommand Type Example Minimum Wait Time1• Control command (Run, Stop)• Set inputs/outputs• Read monitors and parameter values5 ms <1>2 Write parameters 200 ms <1>3 Save changes using an Enter command 200 ms to 2 s, depending on the numberof parameters that were changed <1>4 Enter with storage to drive EEPROM after initialization 5 s<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 messageController →Bypass Controller→BypassBypass →Controller24 bit length Master SendWait TimeTimeFigure D.4 Minimum Wait Time for Sending MessagesSet a timer in the master to check how long it takes for the slave bypass(es) to respond to the master. If no response is receivedwithin a certain amount of time, the master should try resending the message.u Response Messages from Bypass to MasterIf the bypass receives a command from the master, it will process the data received and wait for the time set in Z3-07 until itresponds. Increase Z3-07 if the bypass response causes overrun in the master.TimeCommand message Response message Command messagePLC→Bypass PLC→BypassBypass→PLC24-bit length Z3-07settingFigure D.5 Minimum Response Wait TimeD.6 Communications TimingYASKAWA ELECTRIC SIEP YAIZ1B 01E YASKAWA AC Drive – Z1000 Bypass Technical Manual 387D MEMOBUS/ModbusCommunications
