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9
COMMUNICATION
9.1
Communication Protocol
CL551 is equipped with a RS232 bi-directional , half-duplex interface as standard.
Baud rate is set at 9600 baud as default. You can modify it through keyboard selecting following rate : 300, 600, 1200,
2400, 4800, 9600 and 19200 baud. Transmission parameters are 8 bit length, no parity and 1 bit stop. Address can be
modified through keyboard and it is set 1 as default. RS232 interface connector is a 9 pin DB9 male connector.
Cable connection to a standard personal computer as follows :
9 pin CL551
9 pin PC connector
2 ----------------------------------------> 3 --------------------------> 2
3 ----------------------------------------> 2 --------------------------> 3
5 ----------------------------------------> 5 --------------------------> 7
Communication protocol is based on Answer to Request system.
CL551 will answer only if you sent a Request to it.
There are two kind of request :
RVAR to read a variable.
WVAR to set a variable.
9.2
Reading a variable
The instruction to read a variable has to be an ASCII code composed as follows :
$ character
Instrument Address
RVAR request string
Variable Index
Blank space
Carriage Return
For example, if the set point has to be read (Variable index = 0), supposing the instrument address to be 1:
$1RVAR0 \r
ASCII code
$
HEX $ code
24
The answer of the CL551 will be as follows
* character
Carriage return
* character
Instrument Address
Answer string
Carriage Return
For example if set point is 50.5 °C , supposing the instrument address to be 1:
ASCII code *
\r
*
HEX
$
2A
0D
2A
code
List of Variable Index available
Variable
Actual Setpoint
Ramp : ON /OFF
1
R
V
A
R
31
52
56
41
52
1
S
P
31
20
53
50
20
Index
0
1
25 pin PC connector
0
\r
30
20
0D
:
0
0
20
3A
20
30
30
22
5
0
.
5
\r
35
30
2E
33
0D
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