Manual

15
CMVLC401A
Commissioning
6 LECOM Message Details
6.1 Telegram Response
The SMV controller must return an acknowledgement to the host. The only exceptions to this are when a broadcast
telegram is received or when the controller address is not correct. These telegrams do not require an acknowledgement.
The SMV controller sends two types of acknowledgements:
• Negative acknowledgement (NAK = 15hex), if:
− a fault (e.g. parity fault) was detected in one or more characters, including the character ENQ
− an invalid command or variable address has been recognized
− the variable value is not within the permissible range
• Otherwise, Positive acknowledgement (ACK = 06hex)
6.2 Receive Telegram
The command RECEIVE is to request parameter values of the SMV controllers. The code numbers of the requested
parameter are transmitted via the RECEIVE telegram using the following structure:
EOT AD1 AD2 C1 C2 ENQ
The abbreviations have the following meanings:
EOT (04
hex
) End of the (previous) transmission
AD1, AD2 Logic unit address of the slave to be addressed Slaves
C1, C2 Code number (two ASCII characters) or extended addressing
ENQ (05
hex
) Station request
6.3 Receive Telegram Response
The SMV controller addressed via a RECEIVE telegram generates one of the following responses:
• The controller could decode the request and is now sending the requested parameter value to the host.
STX C1 C2 V1 O Vn ETX BCC
• The controller could decode the request, however, a check-sum fault (parity fault) occurred during transmission.
STX C1 C2 ? ETX BCC
• The controller could not process the request because the requested code number does not exist.
STX C1 C2 EOT
The abbreviations have the following meanings:
STX (02
hex
) Start of text
C1, C2 Code number (two ASCII characters) or extended addressing
V1 to Vn Parameter value (n ASCII characters)
ETX (03
hex
) End of text
BCC Block-check character (00 ... FF
hex
)
? (3F
hex
) ASCII character “?”
EOT (04
hex
) End of the (previous) transmission
Structure and meaning of the block-check character (BCC) are described in the corresponding paragraph of the chapter
SEND.