GB
DIRIS A40/A41 - RS485 - JBUS/MODBUS
®
9
DIRIS A40/A41 - Ref.: 536 103 B GB
COMMUNICATION
The JBUS/MODBUS
®
used by the DIRIS A40/A41
involves a dialogue using a master-slave hierarchical
structure. There are two possible dialogues:
•themastercommunicateswithaslave(DIRIS� and
waits for its reply
•themastercommunicateswithalltheslaves(DIRIS�
without waiting for their reply.
The mode of communication is the RTU (Remote
Terminal Unit� using hexadecimal characters of at least
8 bits.
According to the JBUS/MODBUS
®
protocol, transmis-
sion time must be less than 3 silences, i.e. the emission
time of 3 characters so that the message is processed
by the DIRIS.
To correctly use information, the following functions
are important:
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.
16 : to write n words (maximum 128�.
NB:
When selecting slave address 0, a message is sent to
all the instruments present on the network (only for
functions 6 and 16).
Comment :
The response time (time out question/answer) is 250 ms
maximum
THE STANDARD COMMUNICATIONS FRAME
Slave address Function code Address Data CRC 16
The standard communications frame consists of:
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