14
ASYNC 232
↔
422/485 CONVERTER
Once you have properly set the configuration switches, you are ready to
connect the Converter to your system. This chapter tells you how to
properly connect the Converter to the RS-485 and RS-232 interfaces.
4.1 Connection to the RS-485 Interface
To function properly, the unit
must
have one or two twisted pairs of metallic
wire. These pairs must be dry (unconditioned) metallic wire, between 19
and 26 AWG solid copper core (not stranded). Note that the higher number
gauges may limit distance somewhat, and unshielded produces better
results than shielded.
The Converter is available with several different physical interfaces on the
RS-485 side: DB25 (following the RS-530 standard) and terminal blocks
with strain relief.
4.1.1 4-W
IRE
C
ONNECTION
U
SING THE
DB25 (IC477A-X-R2
AND
IC478A-X-R2)
The DB25 connector on the Converter’s RS-485 side conforms to the
RS-530 interface standard. When connecting to an RS-485 device that also
conforms to the RS-530 standard, your cable should be “crossed over” in
the manner shown below.
Converter
RS-485 (530) Device
Signal
DB25 Pin
DB25 Pin
Signal
XMTA
2......................................3
RCVA
XMTB
14....................................16
RCVB
RCVA
3......................................2
XMTA
RCVB
16....................................14
XMTB
NOTES
1) In the pinout above “A” means positive and “B” means negative.
4. Installation
