Lumel RE15, User Manual, Page: 7 / 28

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set baud rate accepted on the link.
The frame format is shown below:
Start Address Function Data CRC End
bedinning check index
index
T1-T2-T3-T4 8 bits 8 bits n x 8 bits 16 bits T1-T2-T3-T4
Start and end indexes are marked symbolically as an interval equal
to four lengths of the index (information unit). The checking code
consists of 16 bits and emerges as the result of CRC calculation
(Cyclical Redundancy Check) on the frame contents.
2.3. Characteristic of frame fields
Address field
The address field of a message frame contains two characters
(in ASCII mode) or eight bits (in RTU mode).
Valid slave device addresses are in the range of 0-247 decimal. The
master addresses the slave units by placing the slave
address in the frame address field. When the slave sends its
response, it places its own address in the frame address field what
enables the master to check which slave is responding. The 0
address is used as a broadcast address recognized by all slave
units connected to the bus.
Function field
The function code field of a message frame contains two
characters (in ASCII mode) or eight bits (in RTU mode). Valid codes
are in the range of 1-255 decimal. When a message is sent from a
master to a slave device, the function code field tells the slave what
kind of action to perform. When the slave responds to the master, it
uses the function code field to indicate and confirm either a normal
(error-free) response or that some kind of error occurred and the
realization of the command is impossible.
For a formal response the slave simply echoes the original function
code. In case of an error assertion, the slave returns a special code
that is equivalent to the original function code with its most