INFICON BCG450 ATM to Ultra-High Vacuum Triple Gauge - Manual (Page 34)

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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 Comment
0 Length of data string 7 set value
1 Page number 5 for BCG450
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 Response value 13 for BCG450
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 for BCG450
8 Check sum of bytes 1 … 7 0 … 255 Low byte of check
sum 1)
1) High order bytes are ignored in the check sum.
4.8.1 Description of the
Functions
Operational parameters
Electrical connections
4.8.1.1 Output String (Transmit )
Format of the output string
Synchronization