Cooper Instruments & Systems DFI INFINITY Digital Force Indicator/Controller - Manual (Page 10)

Logic symbols are opto-isolated, and drive power is obtained from a galvanically-isolated transformer winding so
that the differential signals (minimum ±2 V) will not be altered by an external ground; earthing of the external
transceiver power supply is recommended to limit common-mode voltage.
The RS-485 hardware may be operated point-to-point (e.g., as RS-422 equipment), OR in multipoint, sharing
the bus wires with up to 32 other meters.
The RS-485 cabling may be a single pair of wires (usually with a shield) for HALF DUPLEX (Figure 2-6), or two
such pairs for FULL DUPLEX (Figure 2-7). The configurations shown are for bus operation, with tap-offs for
each meter.
Figure 2-6. Multipoint, Half-Duplex RS-485 Connection
Table 2.3-Half-Duplex Hookup (RS-485) to the Computer
METER (DCE)
RJ-12
NEW OLDER PIN SIGNAL/
FUNCTION
RS-485 RS-485 BD
COMPUTER (DTE)
D9/D25
RX+/TX+=RX 2 1 (SEE MFG DWG)
RX-/TX-=TX 3 2 (SEE MFG DWG)
N/C or RTN - 3 (SEE MFG DWG)
RS-422/RS-485 multipoint interconnections between the computer (DTE) and the meter (DCE) are less well
defined because different computer/controller manufacturers use different pins on their D9 or D25 connectors.
Figure 2-7. Multipoint Full-Duplex RS-485 Connection
CF 125 INFINITY SC GUIDE 6 M1519/N/0605