TM 5-3895-374-24-1
Serial Link
Description of
The protocol Is based on the exchange of data comprising ASCII characters, exclusively
the protocol
For the rest of this document, all characters are considered to be encoded In ASCII (see ASCII codes
table, page 120)
The exchanges are of the question-answer type
The master (programmable controller or microcomputer) sends a question to the speed controller and
waits for its answer which should arrive within 50 ms, maximum If this time is exceeded the master
must repeat the question
Failure to respond by the speed controller occurs in the following cases
- Incorrect question format,
- parity error detected in the characters,
- faulty, or interrupted link
Message format
The messages are delimited by a start character
? for a question,
> for an answer,
and two end characters LF followed by CR
Question
Start
Question code
Data 1
Separator
Data 2
End
?
see table
number of word
1or 2 characters
value
<LF> <CR>
or bit
<SP> or <@>
’ These 2 symbols only exist to carry out writing, they are empty if a read request is made
Answer
Start
Question code
Data 3
End
>
see table
value
<LF> <CR>
’ This value only exists In answer to a read request, it is empty If a write request is made
Data 1 bit or word number between 0 and +32767,
the + is optional, as are the leading zeros
Example for word W19, either 19 or +00019
Data 2 value of word or bit to be written
For 1 word whole number between -32768 and +32767,
the + Is optional, as are the leading zeros
Examples 25 or +00025,-168 or-00168
For 1 bit 0or 1
Data 3 value of word or bit to be read
For 1 word 6 characters, fixed format
Examples +00034, -21254
For 1 bit 0 or 1.
(page 3-266)
