HBK AED 9101D, Руководство по эксплуатации

Страница: 28 / 104

AED
CONNECTING INTERFACES AND I/OS
26
7 CONNECTING INTERFACES AND I/OS
Depending on the version, the basic device has different interfaces, which can partially be
operated in different configurations. You also have one or more digital inputs and out­
puts, depending on your AED version. Sections 7.2 to 7.6 show you the various connec­
tion options for the different AED versions. The section below provides general informa­
tion on the various bus systems and connection variants.
7.1 Using several AEDs (bus mode)
7.1.1 Connection variants with the RS-485 interface
Via this interface, up to 89 AEDs can be connected to the same bus line, which may have
an overall length of up to 1000 m. Fig. 7.1 shows the basic layout diagram of bus wiring
for 4-wire mode.
Line termination
Line termination
TB
TA
RB
RA
Master Node 1 Node X
...
500Ω
500Ω
500Ω
500Ω
500Ω
500Ω
500Ω
500Ω
+5 V
+5 V
+5 V
+5 V
TxD RxD
TB TA
T R
RB RA
TxD RxD
TB TA
T R
RB RA
TxD RxD
TB TA
T R
RB RA
GND
GND
GND
GND
Fig. 7.1 Bus layout for a 4-wire bus with RS‐485
To ensure the interface functions perfectly, the termination resistors shown in Fig. 7.1,
which have 500
Ω
, have an important role at the (physical) ends of the bus system. These
resistors 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 (bus termination, i.e. the PC and AED 89 in Fig. 7.1. If necessary, slide the
bus termination switch on the AED9101D to on and activate the resistors with the bus