Communication - Bticino Modbus RS485 Manual De Instalación

Communication

The MODBUS® used by the F3N400 or F3N500 product involves a dialogue using a master-slave hierarchical structure.
There are two possible dialogues:
• the master communicates with a slave (F3N400 or F3N500 product) and waits for its reply.
• the master communicates with all the slaves (F3N400 or F3N500 product) without waiting for their reply.
The mode of communication is the RTU (Remote Terminal Unit) using hexadecimal characters of at least 8 bits.
The standard communications frame
The standard communications frame consists of:
Slave address
According to the MODBUS® protocol, transmission
time must be less than 3 silences, i.e. the emission
time of 3 characters so that the message is processed
by the F3N400 or F3N500 product.
To use this information correctly, it is indispensable that
the functions be used in accordance with the codes:
3: to read n words (maximum 128).
6: to write one word.
8: to diagnose exchanges between the master and the
slave via meters 1, 3, 4, 5 and 6.
10: to write n words (maximum 128).
Communication table
> The communication tables are available on the CD-Rom supplied with the RS485 MODBUS® module for F3N400 or F3N500
product.
24
Function code Address Data
NB:
1 word <=> 2 octets <=> 16 bits
2 words <=> 4 octets <=> 32 bits
When selecting slave address 0, a message is sent to all the ins-
truments present on the network (only for functions 6 and 16).
Comment:
The response time (time out question/answer) is 250 ms
maximum.
CRC 16