The pull-up and the pull-down resistors are included inside the processor mod-
ule's serial RS-485 adaptor. The termination resistor is not included inside the
processor module and must be connected externally.
It is useful to activate both the pull-up and the pull-down resistors, which are only necessary
once on every bus line, at the bus master. For this reason, these 2 resistors are already inte-
grated within the COM2 interface of the processor module. They can be activated by connecting
the terminals 1-2 and 3-4 of COM2.
For equipping AC500-eCo processor modules with a real-time clock and a
second serial RS-485 interface COM2, use TA562-RS-RTC serial RS-485 and
real-time clock adaptor
Ä
Chapter 2.5.5.6 “TA562-RS-RTC - Adaptor with Serial
RS-485 (COM2) and Real-time Clock ” on page 1233.
Table 209: Pin assignment
Serial Interface Pin Description
1 Terminator P
2 TxD/RxD-P
3 TxD/RxD-N
4 Terminator N
5 Functional earth
The following figure shows an RS-485 bus with the bus master at the line end.
1 Master at the bus line end, pull-up and pull-down activated, bus termination with 120 Ω
resistors
2 Slave within the bus line
3 Slave at the bus line end, bus termination with 120 Ω resistors
If the master is located within the bus line, it does not need a terminating resistor. The pull-up
and the pull-down resistors, however, are necessary:
1 Slave at the bus line end, bus termination with 120 Ω resistors
2 Master within the bus line, pull-up and pull-down activated
3 Slave within the bus line
4 Slave at the bus line end, bus termination with 120 Ω resistors
System Assembly, Construction and Connection
AC500-eCo > Connection and Wiring
2019/04/17 3ADR010121, 13, en_US 1213
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