FISCHER Mess- und Regeltechnik GmbH
Parameterization | 5
BA_EN_EA16
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RTU Framing (t3.5)
Frame 1
3.5 char
3.5 char
4.5 char
Frame 2
3.5 char
Frame 3
t
0
Starting
≥3.5 char
Address
8 bit
Function
8 bit
Data
N x 8 bit
CRC Check
16 bits
End
≥3.5 char
Modbus message
Fig. 102:
Modbus Message Frame
In slow networks it may be necessary to prolong the time interval t3.5. Entries
stated in ms.
t3.5 =
Number of bits
Baud rate
x 3500 [ms]
Fig. 103:
Conversion t3.5 in ms
Usually, a bit sequence comprises 11 bits. Due to the fact that two stop bits are
also approved for the parity check, the number of bits may sometimes be 12.
The calculated value t3.5 in ms is the lower limit that may not be undercut. Only
inputs larger than this value will prolong the time interval.
