INFICON HPG400 ATM to High-Vacuum Gauge - Manual (Page 28)

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tina31e1 (2004-05) HPG400 v1.om
The built-in RS232C interface allows transmission of digital measurement data and
instrument conditions as well as the setting of instrument parameters.
Caution
Caution: data transmission errors
If the gauge is operated with the RS232C interface and a fieldbus in-
terface at the same time, data transmission errors may occur.
The gauge must not be operated with the RS232C interface and
DeviceNet or Profibus at the same time.
The interface works in duplex mode. A nine byte string is sent continuously without
a request approx. every 20 ms.
Commands are transmitted to the gauge in a five byte input (receive) string.
• Data rate 9600 Baud set value, no handshake
• Byte 8 data bits
1 stop bit
• TxD Pin 13
• RxD Pin 14
• GND Pin 5
(Sensor cable connector)
The complete output string (frame) is nine bytes (byte 0 … 8). The data string is
seven bytes (byte 1 … 7).
Byte No. Function Value
0 Length of data string 7 (Set value)
1 Page number 5 (Set value)
2 Status
→ Status byte
3 Error
→ Error byte
4 Measurement high byte 0 … 255
→ Calculation of pressure value
5 Measurement low byte 0 … 255
→ Calculation of pressure value
6 Software version 0 … 255
→ Software version
7 Sensor type 11 (For HPG400 gauges)
8 Check sum 0 … 255
→ Synchronization
Synchronization of the master is achieved by testing three bytes:
Byte No. Function Value Comment
0 Length of data string 7 (Set value)
1 Page number 5 (Set value)
8 Check sum of bytes No. 1 … 7 0 … 255 Low byte of
check sum
1)
1)
High order bytes are ignored in the check sum.
4.5 RS232C Interface
4.5.1 Description of the
Functions
Operational parameters
Electrical connections
4.5.1.1 Output String (Transmit )
Format of the output string
Synchronization