IAI America TTA - Manual (Page 11)

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Header:
Indicate the start of a command/response message. The header specifies one of the following message
categories:
‘!’ (21H) - - - Command
‘#’ (23H) - - - Normal response
‘&’ (26H) - - - Error response
Station: Indicate the station number of the controller (value of “I/O parameter No. 91: User-open SIO channel xx,
station code). (xx in "I/O parameter No. 91: User-open SIO channel xx, station code" above denotes a
channel number. For details, see page 7.)
Message ID: A three-digit hexadecimal code indicates the message type. (Refer to 4-1, “Message List.”)
Message content: Set data varies with each message. (Refer to 4-3, “Message Details,” for details on each message.)
SC: Checksum
CR (0DH):
Indicate the end of a command/response.
LF (0AH): Indicate the end of a command/response.
Calculation of Checksum (SC)
A checksum is used to verify if the communication has been successful. The communication is deemed successful if the
checksum calculated from the received data is the same as the checksum in the message. Each checksum is an ASCII code
representing the lower byte of the total sum calculated by adding the message values represented in one byte length from the
beginning of the message to immediately before the checksum. You can disable the controller’s checksum function by entering
‘@@’ as the checksum.
Example: Effective Position Data Query
Total sum = 21H+39H+39H+32H+30H+39H
+30H+30H+31H+30H+30H+35H
= 254H
The checksum is calculated as ‘54.’
‘!’ ‘99’ ‘209’ ‘001’ ‘005’ SC CR LF
21H 39H 39H 32H 30H 39H 30H 30H 31H 30H 30H 35H 0DH 0AH
35H
( '5' ) 34H
( '4' )