Hardy Process Solutions HI 2160RC PLUS, Operation And Installation Manual

Page: 144 / 220

Chapter 7 - Serial Communications
7-5
Data Transmission
Format 1. Mnemonics for outgoing command format.
NOTE: Some of the mnemonics are optional.
TABLE 7-2: OUTGOING COMMAND FORMAT
MNEMONIC MEANING NUMBER OF ASCII BYTES
CMD Command 1
SUB-CMD Sub-Command 1 to 3
DATA-n Data Byte n 1 to 6
MODE Mode 1
CR Carriage Return 1
a. Serial commands are transmitted from the host to the controller
(in ASCII bytes) in the format used in the example below:
START
CHAR
INSTRUMENT
ADDRESS
CMD SUB-CMD
6 BYTE DATA
D6 ... D1
MODE CR
2 BYTE CHECKSUM
EOT
CHK-1 CHK-2
> 10 X G CR CHK-1 CHK-2 EOT
NOTE: The example uses decimal and mnemonic abbreviation format for clarity; however,
the actual data would be in ASCII format.
b. There is one space (20 hex) required between each type of data
following the INSTRUMENT ADDRESS. The outgoing com-
mand represented in hex format would be:
3E313020582047200D364404
• This Represents:
3E 31 30 20 58 20 47 20 0D 36 44 04
-For-
> 1 0 X G CR 6 D EOT
• The checksum is computed by totaling the bytes in the
command stream starting with the INSTRUMENT
ADDRESS through (and including) the CR and then sub-
tract 256 from the total until the remainder is less than 256
(to achieve a one byte maximum).
• The result is then represented as two ASCII bytes and
appended to the command, followed by an EOT (04)
•