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RUDOLF - Ref. : CDR 27 028_gb
R-DPA96 A/AN - RS485 - JBUS/MODBUS
®
COMMUNICATION
The JBUS/MODBUS
®
used by the R-DPA96 A/AN
involves a dialogue using a master-slave hierarchical
structure. There are two possible dialogues:
• the master communicates with a slave (R-DPA96)
and waits for its reply
• the master communicates with all the slaves (R-
DPA96) 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, transmission
time must be less than 3 silences, i.e. the emission time
of 3 characters so that the message is processed by
the R-DPA96.
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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