10
Command/Response Formats Section 2-2
• FCS: The 2-character FCS (frame check sequence) is returned.
• Terminator: Two characters indicating the end of the command, “*” and
CR (CHR$(13)), are returned.
Error Response Formant If a reception error or an error in executing the command occurs, a response
is returned with no text.
Partitioned Commands If a command is longer than 131 characters, the command’s text is partitioned
by sending a delimiter [CR code, CHR$(13)] instead of a terminator at the end
of each command frame until the last one. A terminator is sent at the end of
the last frame. The procedure is given below for three command frames.
Note When sending command frames for writing (WR, WL, WC, WD, etc.), be care-
ful not to partition into separate frames data that is to be written into the same
word.
1,2,3... 1. From the host computer, attach a delimiter (CR) at the end of command
frame 1 and send the frame.
2. When the PLC receives this delimiter (CR), it will return only a delimiter
(CR) to the host computer.
3. From the host computer, attach a delimiter (CR) at the end of command
frame 2 and send the frame.
4. When the PLC receives this delimiter (CR), it will return only a delimiter
(CR) to the host computer.
5. From the host computer, attach a terminator (*CR) at the end of command
frame 3 and send the frame.
6. When the PLC receives this terminator (*CR), it will return the response
format with a terminator (*CR) attached to the end.
Unit number (BCD)
End code (hexadecimal)
FCS
Terminator
Header code
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