Specifications

Command Set 4-3
appears when large data values saved in the module’s EEPROM are read
back. In most practical applications, the problem is non-existent.
Overload values of analog data are +99999.99 and -99999.99 .
Data read back from the Event Counter with the Read Events (RE)
command is in the form of a seven-digit decimal number with no sign or
decimal point. Round-off errors do not occur on the event counter. For
example:
Command: $1RE
Response: *0000123
The Digital Input, Digital Output, and Setup commands use hexadecimal
representations of data. The data structures for these commands are
detailed in the command descriptions.
Write Protection
Many of the 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. They 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 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 20 printable characters. If
a properly addressed module receives a command message of more than
20 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 from the module begin with either an asterisk ‘ * ‘
(ASCII $2A) or a question mark ‘ ? ‘ (ASCII $3F) prompt. The ‘ * ‘ prompt
indicates acknowledgment of a valid command. The ‘ ? ‘ prompt precedes
an error message. All response messages are terminated with a CR. Many
commands simply return a ‘ * ‘ character to acknowledge that the command
has been executed by the module. Other commands send data information