YASKAWA LA500, Technical Manual

Page: 139 / 376

Network
Communications
6
6.1 MEMOBUS/Modbus Communications
YASKAWA SIEPYEULA5001C LA500 Technical Manual 139
This section gives information about message timing.
■
Command Message from Master to Slave
To prevent data loss and overrun, after the master receives a message from the slave, the master cannot send the
same type of command message to the same slave for a selected length of time. The minimum wait time is
different for each type of message. Refer to
Table 6.3 to find the minimum wait times.
Table 6.3 Minimum Wait Time to Send a Message
Command Type Example Minimum Wait Time
1
• Operation commands (Run command, stop command)
• I/O settings
• Reading the motor and parameter setting values
5 ms
*1
2 Writing a parameter 50 ms
*1
3 Writing of modified data with the Enter command 3 to 5 s
*1
*1 When the drive receives a message in the minimum wait time, it does command type 1 and sends a response message. If the drive
receives command type 2 or command type 3 messages in the minimum wait time, it will trigger a communications error or the drive
will ignore the command.
Figure 6.5 Minimum Wait Time to Send a Message
You must set the timer in the master to measure the length of time for the slave to respond to the master. If you set
the timer, but the slave does not send a response message in a specified length of time, the master will send the
message again.
■
Response Message from Slave
The slave receives the command message from the master then processes the data it received. The slave then waits
for the time set in
H5-06 [Drive Transmit Wait Time] then sends a response message to the master. If overrun
occurs on the master, increase the wait time set in H5-06 .
Figure 6.6 Response Wait Time
◆
Message Format
■
Communication Message Description
In MEMOBUS/Modbus communications, the master sends commands to the slave, then the slave responds. The
master and slave send their messages in the configuration in
Figure 6.7 . The length of the data changes when the
description of the command (function) changes.
Figure 6.7 Message Format