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MODBUS
RS485/RS232 Communications Interface
Typical Transmission Line Activity
This diagram illustrates a typical sequence of events on a Modbus transmission line.
Period “a”
The processing time (latency), required by the Slave to complete the command
and construct a reply. This is typically 2 milliseconds.
Period “b”
The processing time required by the Master to analyse the Slave response and
formulate the next command.
Period “c”
The wait time calculated by the Master for the Slaves to perform the operation.
None of the Slaves will reply to a broadcast message.
Master
Slave 1
Master
Slave n
Master
Reply
a
a
c
Broadcast
b
To Slave n
b
a
a
Reply
To Slave 1
Activity
Master
Slave 1
Slave n
Network
Time
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