To daisy chain SBCs:
1.
Use P1 and P2. (They are two of three blue connectors on
the back side of the logic board.) P1 is the exit connector
and P2 is the entry connector. See figure 4.23.
2.
Connect a low capacitance cable for EIA RS-485 standard
(2 pair twisted 24 gauge/stranded conductors (7x32). e.g.,
Belden #1419A= NEC:CM PCC FT 1) from the + on the
exit connector of the SBC to the + on the entry connector
of the next SBC in the chain. Do the same for - and GND.
3.
Use figure 4.23 as a guide for linking all SBCs, except the
first and final SBCs in the chain.
4.
The final SBC in the chain must be terminated with a 120
ohm resistor as shown in figure 4.24.
4-17
Options
figure 4.23 Beginning connections in an SBC chain
figure 4.24 Final SBC in chain
