Omega A2400 - Manual (Page 26)

Command Set 4-5
Example: Append a checksum to the command $1WE
Characters: $ 1 W E
ASCII hex values: 24 31 57 45
Sum (hex addition) 24 + 31 + 57 + 45 = F1
The checksum is F1 (hex). Append the characters F and 1 to the end of the
message: $1WEF1
Example: Verify the checksum of a module response *1WEF7
The checksum is the two characters preceding the CR: F7
Add the remaining character values:
* 1 W E
2A + 31+ 57+ 45 = F7
The two lowest-order hex digits of the sum are F7 which agrees with the
transmitted checksum.
Note that the transmitted checksum is the character string equivalent to the
calculated hex integer. The variables must be converted to like types in the
host software to determine equivalency.
If checksums do not agree, a communications error has occurred.
If a module is setup to provide linefeeds, the linefeed characters are not
included in the checksum calculation.
Parity bits are never included in the checksum calculation.
A2400 User Commands
Table 4.1 shows all the A2400 commands. For each case, a typical
command and response is shown. Note that some commands only respond
with an * as an acknowledgment. Table 4.1 also separates write protected
commands from commands that are not write protected.
For clarity, Table 4.1 separates A2400 Extended Address mode commands
from other commands. Note that the Extended Address commands use a
different prompt and a two character address.