Connecting Pfeiffer Vacuum display and control units or a PC
One external control unit each can be connected at the RS-485 interface.
1. Use the respective connection cable from the control unit shipment or from the accessories pro-
gram.
2. Use the option to connect a PC via the USB/RS-485 converter.
6.3 Cross-linked via the RS-485 connection
DANGER
Danger to life from electric shock
When establishing the voltages that exceed the specified safety extra-low voltage (according to IEC
60449 and VDE 0100), the insulating measures will be destroyed. There is a danger to life from elec-
tric shock at the communication interfaces.
► Connect only suitable devices to the bus system.
Y connector
RS-485
RS-485
M12
M12
M12
USB/RS-485 converter
MVP
MVP
MVP
Fig. 9:
Networking via the RS-485 interface
6.4 Pfeiffer Vacuum protocol for RS-485 interface
6.4.1 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
a2 – a0
Unit address for slave
● Individual address of the unit ["001";"255"]
● Group address "9xx" for all identical units (no response)
● Global address "000" for all units on the bus (no response)
*
Action according to telegram description
n2 – n0
Pfeiffer Vacuum parameter numbers
I1 – I0
Data length dn to d0
dn – d0
Data in the respective data type
(see chapter “Data types”, page 28)
.
Interfaces
26/54
