RS-485 cables - WMT700

WMT700 Series User Guide

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User guide

In the RS‑485 mode, the same signals as in the RS‑422 mode are available at the end of cables 2 m, 10 m, 15 m, and 26 m. Make 2‑wire loop-backs at the end of the cable or connect the wires to the same terminal.

Figure 1. COM2 RS‑485 wiring
Table 1. RS‑485 wiring
WMT700 signals Wire colors WMT700 M23 connector pin RS‑485 signals
RxA / RX− Green 3
TxA / TX− Orange 4
TxB / TX+ White/orange 14 +
RxB / RX+ White/green 15
To avoid confusion, the RS-485 and RS-422 signals of WMT700 are named as follows:
  • Inverting: –
  • Non-inverting: +

According to the EIA-485 standard, the lines are named as follows:

  • Inverting: – <=> A
  • Non-inverting: + <=> B

The A/B naming used by some manufacturers is in conflict with the standard. To ensure proper operation, verify the polarity of the signals when using the device on the bus with signals named as A/B. Opposite polarity causes data inversion on the bus, but it does not damage the device.