FC 300 Design Guide
How to Program
" Serial communication via RS 485 Interface
" Protocols
Master-slave communicat ion.
" Telegram Traffic
C
ontrol a nd response teleg rams
The master controls telegram traffic in a master-slave system. You can connect a maximum of 31 slaves to
a master unless you use repeaters. If so, you can connect a maximum of 126 slaves to a master.
The master constantly sends telegrams addres sed to the slaves and waits for their response
telegrams. The s lave response time is maximum 50 m
s.
A s lave can only send a response teleg ram if it has
received an error-free telegram addressed to itself.
B
roadcast
A master can send the same telegram simultaneously to all slaves connected to the bus. During this broadcast
communication, the slave does not send any response telegrams to the master on whether the tel egram is
correctly received. Broadcast communi
cation is set up in add ress format (ADR), see Telegram struct ure.
C
ontent of a ch aracter (byte
)
Each characte
r transferred begins with a start bit.
Then 8 data bits are transferred, corresponding to
a byte. Each character is secured via a parity bit,
which is s
et to "1" when it reaches parity (i.e. when
there is a n equal numbe r of 1’s in the 8 data bits
and the parity bit in total). A character is completed
by a s t
op bit, thus consisting of 11 bits in all.
" Telegram Structure
Each telegram begins with a start character
(STX) = 02 Hex, follow ed by a byte denoting
the telegram length (LGE) and a byte denoting
the adjustable frequency drive addre ss (ADR).
A number of data bytes (variable, depending on
thetypeoftelegram)follow. Thetelegramis
completed by a data control byte (BCC).
*
default setting ()display text []value for use in communication via serial communication port
269
MG.33.B
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