CIRCUTOR DHB Series - Manual (Page 27)

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tection terminal (it is not necessary for a correct interface work).
To obtain the connection with a computer of IBM PC class, a RS-485
card or a RS-232/RS-485 converter is indispensable.
The connection way of devices is shown on the fig. 10
The designation of transmission lines for the card in the PC komputer
depends on the card producer.
6.2. Description of the MODBUS Protocol
Implementation.
The implemented protocol is in accordance with the PI-MBUS-300 Rev
G of Modicon Company specification.
Set of the serial link parameters of meters in MODBUS protocol:
• meter address
1...247,
• baud rate 4800, 9600, 19200, 38400 bit/s,
• work modes RTU,
• information unit RTU: 8N2, 8E1, 8O1, 8N1,
• maximal response time 1000 ms
• The maximum number
of read records in one query: - 60 registers – 4 bytes,
- 120 registers – 2 bytes.
Parameter configuration of the serial link is described in the further
part of the user’s manual. It consists on the settlement of the baud rate
(bAUd parametr), device address (Addr parameter), and the type of
the configuration unit (Mode parameter)
Notice:
Each meter connected to the communication network must have :
• unique address, different from addresses of other devices
connected to the network,
• identical baud rate and type of information unit.