Siemens PGC 302 Edition II - Various Serial Interfaces

VARIOUS SERIAL INTERFACES
The term Serial interface only describes that letters
are transmitted as a succession of bits. The electri-
cal properties of the various serial interfaces are
very different. The chromatograph and control unit
use the following serial interfaces:
TTY
,
V.24
or
RS232
,
RS485
.
TTY interface
The TTY interface operates with a constant current of
20 mA. There is a transmit loop and a receive loop. The
partner which provides the current sources is referred to
as active. The chromatograph is normally switched to
passive.
The control unit requires a converter because it does not
possess a TTY interface. It is switched to active.
V.24/RS232 interface
The RS232 interface operates with ±12 V voltage sig-
nals relative to ground. There is one transmit line and
one receive line. The transmitter always has a voltage
source.
RS485 interface
The RS485 interface operates with a 5-V differential
voltage between two lines. All transmitters and re-
ceivers use these two lines: the partners must agree on
who can transmit when! Each partner has a voltage
source.
The control unit requires an interface converter because
it does not possess an RS485 interface. This is fitted to
the interface plug at the PC. It converts an RS232 inter-
face into an RS485 interface.
Terminators: the first and last partners must be termi-
nated by 120 Ω (jumper on PCPU-2).
Data TTY RS232 RS485
Interference resistance
Networking
Max. number of chromatographs
Max. transmission rate
Max. cable length
Very good
Yes
6
9600 bit/s
200 m distance
Moderate
No
1
38400 bit/s
15 m
Very good
Yes
32
38400 bit/s
1300 m (standard!)
Chromatograph-interface
Use
SER.1 and SER.2
- ChromLAN network
SER.1
- Printer
SER.2
- Local operation
SER.3 and SER.4
- Control system
SER.3 and SER.4
- ChromLAN network
- Control system
+12 V
- 12 V
Time
Voltage
Transmitter
Receiver
Transmitter
Receiver
Control unit Chromatograph
12 V
12 V
20mA
0 mA
Time
Control unit Chromatographs
Transmitter
Receiver
20mA
Receiver
Transmitter
20mA
5 V
Time
Voltage
Control unit Chromatographs
RR
TTY
RS232
RS485
Transmitter
Receiver
Transmitter
Receiver
Transmitter
Receiver
Networking
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2VERNETZ.CHP, Stand Dezember 22, 1999