Lumel RE15, Руководство пользователя, Страница: 10 / 28

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2.6. Character format during serial transmission
In the MODBUS protocol, characters are transmitted from the
lowest to the highest bit.
Organization of the information unit in the ASCII mode:
v
1 start bit,
v
7 data field bits,
v
1 even parity check bit (odd) or lack of even parity check bit,
v
1 stop bit at even parity check or 2 stop bits when lack of even
parity check.
Organization of the information unit in the RTU mode:
v
1 start bit,
v
8 data field bits,
v
1 even parity check bit (odd) or lack of even parity check bit,
v
1 stop bit at even parity check or 2 stop bits when lack of even
parity check.
2.7. Transaction interruption
In the master unit the user sets up the important parameter which is
the „maximal” response time on the query frame” after which
exceeding, the transaction is interrupted. This time is chosen such
that each slave unit working in the system (even the slowest)
normally will have the time to answer to the frame query.
An exceeding of this time attests therefore about an error and such
treated by the master unit.
If the unit slave will find out a transmission error it does not
accomplish the order and does not send any answer. That causes
an exceeding of the waiting time after the query frame and the
transaction interruption.
In the R15 controller „ maximal response time on the query frame” is
equal 1 s.