The interface designated “RS-485” is intended for connecting a Pfeiffer Vacuum control unit or a exter-
nal PC. The connections are galvanically safe and are isolated from the maximum supply voltage for the
electronic drive unit.
Designation
Value
Serial interface
RS-485
Baud rate
9600 Baud
Data word length
8 bit
Parity
none (no parity)
Start bits
1
Stop bits
1
Tbl. 9:
Features of the RS-485 interface
Connecting Pfeiffer Vacuum control units or a PC
► Use the connection cable from the scope of delivery of the control unit or from the
.
► Connect a control unit to the RS-485 interface.
► Connect a PC via the USB/RS-485 converter.
PC
D-Sub
1
2
3
4
Fig. 14:
Cross-link via connection RS-485 using connection cables and accessories
1 RS-485 to M12 adapter
3
M12 to M12 interface cable
2 Y-connector for RS-485
4
USB RS-485 converter
Networking as RS-485 bus
The group address for the electronic drive unit is
902
.
1. Install the devices according to the specification for RS-485 interfaces.
2. Make sure that all devices connected to the bus have different RS-485 device addresses
[P:797]
.
3. Connect all devices with RS-485 D+ and RS-485 D- to the bus.
6.3 Pfeiffer Vacuum protocol for RS-485 interface
6.3.1 Telegram frame
The telegram frame of the Pfeiffer Vacuum protocol contains only ASCII code characters [32; 127], the
exception being the end character of the telegram C
R
. Basically, a master
(e.g. a PC) sends a tele-
gram, which a slave
(e.g. electronic drive unit or gauge) responds to.
a2
a1
a0
*
0
n2
n1
n0
l1
l0
dn
...
d0
c2
c1
c0
C
R
Interfaces
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