KB013 How long can the RS-422 / RS-485 or SSI signal cable be? [ja]

RS-422 / RS-485 and SSI are differential serial data interfaces designed for long data cables. The cable length depends on the cable quality and data rates.
See the following guidelines for the RS-422 / RS-485 interfaces:

  • 19’200 Baud → up to 1000m
  • 115’200 Baud → up to 500m

See the following guidelines for SSI interfaces:

  • ≤ 100kBit/s → up to 1000m
  • ≤ 500kBit/s → up to 200m
  • ≤ 1000kBit/s → up to 100m

Cable type and termination:

  • Use only shielded twisted pair cables
  • Termination according to characteristic impedance of the cable (typically 100 – 150 Ω)

The cable length is also influenced positively / negatively by other factors:

  • Quality of the cable (shielding, cross-section, wire resistance, etc.)
  • Environmental conditions (Disturbance sources like motors, etc.)

Further details in the Technical Reference Manual (see Downloads).