Advent Communications
209297 – DCU5000 Drive Control Unit Page 21 of 42
CHECKSUM
The CHECKSUM is one byte in size and is included for error detection. It is the modulo
addition of all ADDRESS and DATA bytes.
Here is a typical example calculation:
[STX][BYTE COUNT][ADDRESS][DATA..…][CHECKSUM][ETX]
[2] [8] [5] [97 98 99] [43] [3]
The checksum is calculated as follows:
CHECKSUM = (5 + 97 + 98 + 99) mod 256 = 43
ETX (end of transmission)
ETX is the ASCII character 3. It is one byte in size and is used to represent the end of
each message.
5.4. COMMANDS, QUERIES AND RESPONSES
5.4.1. DEFINITIONS.
A command is an instruction sent from the remote controller to the unit to change
some operating parameter or display mode.
A query is an instruction sent from the remote controller to the unit for the unit to report
one, or many, operating parameter.
A response is some data sent from the unit to the remote controller that gives the
answer to a query.
5.4.2. RESPONSE TO VALID COMMANDS
The response to a valid remote command is an echo back of the command (with
associated parameters). This indicates that the command has been accepted and the
unit will attempt to action the command.
Note: Receiving a response of this type does not mean that the command has been
actioned. Generally, the action will occur after the response has been sent. This is to
ensure that all responses are returned quickly. (Average response time <300ms). If
you want confirmation that a change has taken place, you must send a query and then
look at the response.
Example
Command to set the transmit gain to -20.0dB.
The command is ‘GT’ and the valid range for the parameters is 000 to 400.
Command sent GT200
Response from unit GT200
Result – this response indicates that the unit will set the transmit gain to –20.0dB
5.4.3. RESPONSE TO INVALID COMMANDS
A message can be invalid for two reasons: invalid command and invalid parameters
Error 1 – invalid command
If the command is invalid, the response will be the first character of the command sent
followed by “Error”
Example
Command to set the transmit gain to -20.0dB.
The command is ‘GT’ and the valid range for the parameters is 000 to 400.
Command sent G200
Response from unit G Error
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