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PHOENIX CONTACT 105542_en_05
5.2 Setting telegram pauses based on the example of
Modbus/RTU
A frame is also referred to as a telegram. The length of the transmission pause between the
telegrams depends on the set data rate. The beginning and end of a telegram is recognized
by means of a time condition. A pause of 3.5 characters means that the telegram is com-
plete and the next character is to be interpreted as the slave address. A telegram must
therefore be sent as a continuous stream of data. If there is an interruption of more than
1.5 characters within a telegram, the data will be discarded by the receiver.
If the master is not able to transmit the successive characters quickly enough and commu-
nication is aborted, you must increase the minimum pause time (T
FrameEnd
) between the in-
dividual characters of a telegram.
• To adapt data transmission to other protocols, you can adjust the T
FrameEnd
and T
IdleMin
parameters accordingly. Set the interface parameters under “Individual Settings”.
Figure 5-6 PSI-CONF software: “Individual Settings”
Individual settings for frame-based data transmission
Not all of the I/O devices available on the market are verified. In this case, the parameters
must be determined by tests based on the connected I/O device and on the protocol. As
precise protocol knowledge is required, it might be useful to ask an expert for support.
Table 5-1 Verified parameters for frame-based data transmission
Manufacturer Product Protocol T
IdleMin
[bit] T
FrameEnd
[bit]
--PROFIBUS117
--Modbus/RTU3920
Phoenix Contact EMPro Modbus/RTU 56 12
Phoenix Contact SOLAR-
CHECK
Modbus/RTU 56 12
Delta RPI-M20A Modbus/RTU 3 20
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