Appendix 2 Use of MODBUS Communication
84
Setting of these two items for the upper and lower computers should be the same.
Otherwise, communication cannot be established or there will be errors with
communication.
*Note 3: When the driver address is set as 0, the driver will not receive the
communication command, including the broadcast command. When the driver address
is larger than 0, the new address will become effective once it is revised.
*Note 4: To match with other frequency communication command, please set the
frequency communication command unit .For examples, when the frequency of 50HZ
and PLC trasmission frequency of 01F4H is set, 1 is selected. The driver change to
50HZ after receiving the frequency comman; If the transmission frequency is 1388H ,0
is selected and the system deal with it as 50HZ.
Transmission Period Limit
In order to reduce the packet loss ratio caused by the communication disturbance
and get the best communication effect, please limit the data transmission period in
the host station to ensure both data transmission and receiving are normal.
Pb.00 baud
rate selection
Minimum transmission period
limit (ms)
（
only even parity check
）
Suggestion transmission period
limit( ms)
（
all parity check
）
0
：
1200
220ms 250ms
1
：
2400
110ms 150ms
2
：
4800
65ms 100ms
3
：
9600
50ms
90ms
4
：
19200
35ms
80ms
5
：
38400
17ms
50ms
*
Notes
：
With the even parity check manner selected, the user can obtain the quickest
communication response.
The minimum transmission period limit includes the time from the transimisson to
receiving the corret data.
If the transmission period limit is below the minimum transmission period limit, the
main receiving data may be garbled.
Command Formatting
During communication, the main controller (PLC, etc) gives commands to drivers,
and the drivers respond to them. As the command function content varies, the
length of data will vary as well.
The process constitutes the information transmission & receiving as showed in
the following figure. The interval between two commands should maintain the
time recorded below.
Summary of Contents for AS600M Series
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