INFICON SKY CDGxxxD (RS232C) - Manual (Page 6)

6
tira49e1-a (2010-02) RS232C.cp
The example is based on the following output string:
Byte No. 0 1 2 3 4 5 6 7 8
Value 7 2 16 0 125 0 20 6 69
The instrument or controller (receiver) interprets this string as follows:
Byte No. Function Value Comment
0 Length of
datastring
7 (Set value)
1 Page No. 2 CDG025D with output signal 10.24 V
2 Status 16 Pressure unit = Torr
3 Error 0 No Error
4
5
Measurement
High byte
Low byte
125
0
Calculation of pressure value: Conversion
formula
→ 4
6 Read command 20 Software version = 20 / 20 = 1.0
7 Sensor type 6 F.S.R.= 10 +3
8 Check sum 169 2 + 16 + 0 + 125 + 0 + 20 + 6 =
169
dec ≙ 00 A9
hex
High order byte is ignored ⇒
Check sum = A9
hex ≙ 169
dec
Commands to the gauge are transmitted in receipt strings (frames) consisting of
five bytes (without ). The data string is formed by bytes 1 … 3.
Byte No. Designation Value
0 Data string length 3 (constant value)
1 Data → "Service command"
2 Data → "Address byte"
3 Data → "Data byte"
4 Checksum
of bytes No. 1 … 3
Low byte of checksum
1)
1) Possible high bytes are ignored.
• The operation selected in byte No. 1 is addressed in byte No. 2.
• Variables are transmitted in byte No. 3. Variables >1 byte have to be
transmitted in several receipt strings (splitting).
Example
1.2 Receipt String
Structure of receipt string