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VIPA System SLIO
OPTION16: Line assign-
ment
Parameters
Description
00h
None
(Default)
No pre-assignment of the receiving lines.
This setting only makes sense with bus-capable special drivers.
01h
Signal R(A) 5V (Break evaluation)
Signal R(B) 0V
With this pre-assignment break detection is with RS422 possible
at full-duplex operation.
02h
Signal R(A) 0V
Signal R(B) 5V
This pre-assignment corresponds to the idle state (no sender is
activated) at half-duplex operation with RS485. Wire-break recog-
nition is not possible, here.
5.5 Modbus
5.5.1 Basics Modbus
Overview
Master-Slave-Communica-
tion
Telegram-structure
Start ID
Slave address
HB300 | CP | 040-1CA00 | en | 18-28
For a connection with minimum reflections and the break evaluation at RS422/485 opera-
tion, the lines may be preset with defined static voltage levels.
At the CP interface the wiring of the receiver is realized as follows:
Range of values:
00h: none
01h: R(A) 5Volt R(B) 0Volt
02h: R(A) 0Volt R(B) 5Volt
n
Default: 00h
The Modbus protocol is a communication protocol that defines a hierarchic structure
between a master and several slaves. Physically, Modbus transmits via a serial half-
duplex connection as point-to-point connection with RS232 or as multi-point connection
with RS485.
There are no bus conflicts for the master, because the master can only communicate with
one slave at a time. After the master requested a telegram, it waits for an answer until an
adjustable wait period has expired. During the latency the communication with another
slaves is not possible.
The request telegrams of the master and the respond telegrams of a slave have the
same structure:
Function code
Serial communication protocols
Wiring of the receiver
Data
Flow control
Modbus > Basics Modbus
End ID
73
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