AED9101D
24
I3563-1.0 en
be as much as 1000 m. Bus cabling for 4-wire mode is
shown in Fig. 6.10.
Line termination
Line termination
TB
TA
RB
RA
PC = Master
AED 1 = Slave 01
AED 89 = Slave 89
...
500
500
500
500
500
500
500
500
+5V
+5V
+5V
+5V
TxD on/off RxD
TB
TA
T
R
RB
RA
TxD on/off RxD
TB
TA
T
R
RB
RA
TxD on/off RxD
TB
TA
T
R
RB
RA
Fig. 6.10
Bus structure for a 4wire bus with RS485
The termination resistors (termination) of
500
marked
in Fig. 6.10 at the (physical) ends of the bus system are
important for the interface to work perfectly. These resist-
ors ensure interference-free data transmission (no signal
reflections) and defined potentials (voltage levels), if no
data is transmitted over the bus (interface).
The node at the start of the interface cable and the node
at the end of the cable must have resistors available (bus
termination), which in Fig. 6.10 is the PC and AED 89.
The HBM interface converter already contains these bus
termination resistors (cannot be switched off); in the AED
(89 in the example), you must slide the DIP switch for
bus termination to the right (ON) (see Fig. 6.7 on page
20 for the switch position). You must also activate bus