Performance
(Original Document)
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At a Glance
The tables that follow can be used to evaluate typical Modbus communication exchange times according to different criteria.
The results displayed correspond to the average operation period for the READ_VAR function in milliseconds.
Exchange Time Definition
The Exchange Time is the time that passes between the creation of an exchange and the end of that exchange. It includes the serial link communication time.
The exchange is created when the communication function call is made.
The exchange ends when one of the following events occurs:
Exchange Time for One Word
The table below shows exchange times for one word of Modbus communication on a BMX P34 2020 processor:
Exchange time in ms (the Modbus slave is a BMX P34 1000 cyclic)
Cycle time in ms
Cyclic
10
50
Baud rate of communication in bits per second
4800
68
72
100
9600
35
40
50
19200
20
27
50
38400
13
20
50
The BMX P34 2000/2010/20102 processor exchange times are similar to the BMX P34 2020 processor. The BMX P34 1000 exchange times are 10% lower than ones.
NOTE: All exchange times listed above come from measures with an accuracy margin of +/-10 ms.
Exchange Time for 100 Words
The table below shows exchange times for 100 words of Modbus communication on a BMX P34 2020 processor:
Exchange time in ms (the Modbus slave is a BMX P34 1000 cyclic)
Cycle time in ms
Cyclic
10
50
Baud rate of communication in bits per second
4800
500
540
595
9600
280
288
300
19200
142
149
150
38400
76
80
100
The BMX P34 2000/2010/20102 processor exchange times are similar to the BMX P34 2020 processor. The BMX P34 1000 exchange times are 10% lower than ones.
NOTE: All exchange times listed above come from measures with an accuracy margin of +/-10 ms.