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2.0
Operation principles
RS-485 interface is used to two-way simultaneous communication in one pair of
conductors. For this reason, the transmission has to be half-duplex that means
switching off RS-485 transmitter when receiving to allow transmitting to other
communication partners and switching on during its own transmitting only. There
are two methods how to operate the transmitter:
1) The transmitter is controlled from DTE by signal RTS or its invert polarity.
2) DTE does not use RTS (this interface does not dispose this signal or SW does
not use it) and the converter has to interpret its signal TxD automatically. At
the TxD changing moment from idle state (from the negative to positive
polarity), the converter activates the link transmitter automatically. The
transmitter is switched off after the certain time τ of RTS switching off or
TxD return to the neutral polarity. Time interval length τ has to be dependent
on applied transmission rate because in the automatic mode there it is
necessary to keep the transmitter active for the period equal to one byte
transmission time.
In the automatic mode, every device that is to transmit has to wait at least for the
time τ from the last byte recorded on RS-485 bus. If it is to the contrary the first
transmitted byte would be damaged.
3.0
Installation
E06G has to be installed with the respect for specifications of both interfaces.
3.1
Converter connection to RS-232 Interface
Signals assignment to the contacts and DTE-DCE connection is in the table:
SIGNAL
Signal Ground
Transmitted Data
Received Data
Request to Send
Clear to Send
Data Set Ready
Data Terminal Ready DTR
Data Carrier Detect
abbrev
DTE
connector connector
(DB9M)
SG
5
TxD
3
RxD
2
RTS
7
CTS
8
DSR
6
4
DCD
1
3
E06G
transmit direction
(DB9F)
DTE
5
<>
3
output
2
input
7
output
8
input
6
input
4
output
1
input
ELOE06GZKE001
E06G
<>
input
output
input
output
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