System bus connection

 

DFP

GND = System bus reference

SC11 = System bus high

SC12 = System bus low

MOVITRAC® B

GND  = System bus reference

SC22 = System bus outgoing low

SC21 = System bus outgoing high

SC12 = System bus incoming low

SC11 = System bus incoming high

S12   = System bus terminating resistor

 

Please note:

  • Use a 2-core twisted and shielded copper cable (data transmission cable with braided copper shield). Connect the shield flatly on both sides of the electronics shield clamp of MOVITRAC®. Also connect the ends of the shield to GND. The cable must meet the following specifications:
    • Core cross section 0.75 mm2 (AWG18)
    • Cable resistance 120 Ω at 1 MHz
    • Capacitance per unit length ≤ 40 pF/m (12 pF/ft) at 1 kHz
  • The permitted total cable length depends on the baud rate setting of the SBus:
    • 250 kBd: 160 m (528 ft)
    • 500 kBd:   80 m (264 ft)
    • 1000 kBd: 40 m (132 ft)
  • Connect the system bus terminating resistor (S1 = ON) at the end of the system bus connection. Switch off the terminating resistor on the other units (S1 = OFF). The DFP21B gateway must always be connected either at the beginning or the end of the system bus connection and features a permanently installed terminating resistor.

 

INFORMATION

  • There must not be any potential displacement between the units connected with the SBus. Take suitable measures to avoid potential displacement, e.g. by connecting the unit ground connectors using a separate lead.
  • Point-to-point wiring is not permitted.