Port Assignment, Termination, Cable Length
Installation
49
If the cabling of the S
0
bus is realized with two lines, outgoing from the
Forum 523/524 and leading to several IAE sockets, the terminating resistors
(“TR”) in both most distant IAE sockets needs to be switched on. The termi-
nating resistors in the Forum 523/524 must be switched off. The S
0
bus
should not be installed as star topology. Sub-distributions are not allowed
either.
Termination on an IAE socket: IAE sockets with built-in resistors are recom-
mended, because the terminating resistor can be switched on or off with a
mechanical switch. The figure shows how to mount resistors in an IAE socket
without switchable resistors.
You can add S
0
ports by installing appropriate S
0
interface cards in a slot.
These S
0
ports can be switched between internal and external operating
modes.
Pressure terminals are used for internal and external S
0
ports. The
connection assignment of the pressure terminals changes when switched
from internal to external, as shown in the diagram above.
Line termination:
Disabled
IAE
IAE
IAE
1a
1b
2a
2b
TR
TR
S
0
int
2a 2b 1a 1b
1 2 3 4 5 6 7 8
S
0
ext
1a 1b 2a 2b
1 2 3 4 5 6 7 8