INFICON Cube CDGsci (RS232C) - Manual (Page 7)

tira90e1 (2014-01) RS232C.cp
7
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).
For values for byte 1 see parameter table in section 2.
Enter the address of the variable to be read/written (
→ table "Variables for bytes
No. 2 and 3").
When a variable is written (receipt string) the content of byte No. 3 is written to the
variable addressed in byte No. 2 (
→ table "Variables for bytes No. 2 and 3").
When a variable is read (send string), the value of the variable addressed in byte
No. 2 is output in byte No. 6 of the send string. The content of byte No. 3 is not
relevant for read operations.
The checksum is calculated from the sum of byte No. 1 to 3.
The example is based on receive string:
Byte No. 0 1 2 3 4
Value 3 0 2 0 2
The instrument or controller (receiver) interprets this string as follows:
Byte No. Designation Value Comment
0 Data string
length
3 (constant value)
1 Service
command
0 Read command
2 Address byte 2 Filter
3 Data byte 0
4 Checksum 2 0 + 2 + 0 = 2
dec
≙ 00 02
hex
High bytes are ignored

Checksum = 02
hex
≙ 2
dec
1.2 Receipt String
Structure of receipt string
Service command
(byte No. 1)
Address byte
(byte No. 2)
Data byte
(byte No. 3)
Checksum
(byte No. 4)
Example