Pfeiffer Vacuum Protocol for "RS-485"
31
8
Pfeiffer Vacuum Protocol for "RS-485"
8.1
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 message
C
R
. Basically, a master
(e.g. a PC) sends a telegram, which is answered by a slave
(e.g. electronic drive
unit or gauge).
8.2
Telegrams
Data request
?
Control command
!
Data response / control command understood
Error message
8.2.1
Example 1
Data request
Actual rotation speed (parameter
[P:309]
, device address slave: "123")
Data response: 633 Hz
Actual rotation speed (parameter
[P:309]
, device address slave: "123")
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)
*
n2 - n0
Pfeiffer Vacuum parameter numbers
l1 - l0
Data length dn ... d0
dn - d0
Data in data type concerned
c2 - c0
Checksum (sum of ASCII values of cells a2 to d0) modulo 256
C
R
carriage return (ASCII 13)
a2
a1
a0
0
0
n2
n1
n0
0
2
=
?
c2
c1
c0
C
R
a2
a1
a0
1
0
n2
n1
n0
l1
l0
dn
...
d0
c2
c1
c0
C
R
a2
a1
a0
1
0
n2
n1
n0
l1
l0
dn
...
d0
c2
c1
c0
C
R
a2
a1
a0
1
0
n2
n1
n0
0
6
N
O
_
D
E
F
c2
c1
c0
C
R
_
R
A
N
G
E
_
L
O
G
I
C
NO_DEF
The parameter n2 - n0 does not exist
_RANGE
Data dn - d0 are outside the permitted range
_LOGIC
Logic access violation
?
1
2
3
0
0
3
0
9
0
2
=
?
1
1
2
C
R
ASCII
49
50
51
48
48
51
48
57
48
50
61
63
49
49
50
13
1
2
3
1
0
3
0
9
0
6
0
0
0
6
3
3
0
3
7
C
R
ASCII
49
50
51
49
48
51
48
57
48
54
48
48
48
54
51
51
48
51
55
13
