Omega A2400 - Manual (Page 23)

Command Set 4-2
All commands must be terminated by a carriage return character (ASCII
$0D). In all command examples in this text the carriage return is either
implied or denoted by the symbol ‘CR’.
Data Structure
Many commands require additional data values to complete the command
definition as shown in the example commands in Table 4.1. The particular
data necessary for these commands is described in full in the complete
command descriptions.
Write Protection
Some commands listed in Table 4.1 are under the heading of ‘Write
Protected Commands’. These commands are used to alter setup data in the
module’s EEPROM. These commands are write protected to guard against
accidental loss of setup data. All write-protected commands must be
preceded by a Write Enable (WE) command before the protected command
may be executed.
Miscellaneous Protocol Notes
The address character must transmitted immediately after the command
prompt character. After the address character the module will ignore any
character below ASCII $23 (except, of course, CR). This allows the use of
spaces (ASCII $20) within the command message for better readability if
desired.
The length of a command message is limited to 25 printable characters. If
a properly addressed module receives a command message of more than
25 characters the module will abort the whole command sequence and no
response will result.
If a properly addressed module receives a second command prompt before
it receives a CR, the command will be aborted and no response will result.
Response Structure
Response messages begin with either an asterisk ‘*’ (ASCII $2A) or a
question mark ‘?’ (ASCII $3F) prompt. The ‘*’ prompt indicates acknowledg-
ment of a valid command. The ‘?’ prompt precedes an error message. All
response messages are terminated with a CR. Many commands simply
return a single ‘*’ character to acknowledge that the command has been
executed by the module. Other commands send data information following
the ‘*’ prompt. The response format of all commands may be found in the
detailed command description. The maximum response message length is
25 characters.