FC 300 Design Guide
How to Program
" Serial communication via RS 485 Interface
" Protocols
Master-slave communicat ion.
" Telegram Traffic
C
ontrol and response telegrams
The m aster controls te leg ram traffic in a ma ster-slave system. A maxim um of 31 slaves
can be connected to a master w ithout the use of repeaters. Wit
h re peaters it is possible
to conne ct 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 ms.
A s lave can only send a response telegram if it has received an error-free telegram address ed to itself.
B
roadcast
A master can send the same telegram simult
aneously to all slaves connected to the bus. During this broadcast
communication, the slave does not send any re sponse telegrams to the m aster on whether the telegram is
correctly received. Broadcast communic a tion is set up in add ress format (ADR), see Telegram structure.
C
ontent of a ch aracter (byte)
Each character transferred begins w ith a start bit.
Then 8 data
bits are transferred, corresponding to
a byte. Each character is secured via a parity bit,
whichissetto"1"whenitreachesparity(i.e.when
there i
s an equal number of 1’s in the 8 data bits
and the parity bit in total). A character is completed
by a stop b it, thus consisting of 11 bits in all.
" Telegram Structure
Each telegram begins with a start character
(STX) = 0 2 Hex, followed by a byte denoting
the telegram length (LGE) and a byte denoti ng
the adjustable freque ncy drive address (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 c ommunication port
235
MG.33.B
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