Omron CQM1H-SCB41 Operation Manual page 62

Host Link Communications
Communications
Sequence
Frame 1 (command)
@ Unit No.
Header code
Host
Text
computer
FCS
Delimiter
PC
result against the FCS that is included in the frame makes it possible to check
for data errors in the frame.
@ 1 0 R
Node No. Header code
FCS calculation range
ASCII code
@ 40
1 31
0 30
R 52
1 31
Calculation
result
The right to send a frame is called the "transmission right." The Unit that has
the transmission right is the one that can send a frame at any given time. The
transmission right is traded back and forth between the host computer and the
PC each time a frame is transmitted. An example sequence for multiframe
communications between the host computer and PC is described below. Mul-
tiframe communications are handled by exchanging delimiters and then using
terminators to indicate the last frame.
• The host computer sets a delimiter at the end of the first command frame
and transmits the frame.
• When the PC receives the delimiter, it returns the same delimiter to the
host computer.
• After receiving the delimiter from the PC, the host computer transmits the
next frame.
• Delimiters are used to send the rest of the frames.
• When the host computer sends the last command frame, it sets a termi-
nator at the end.
• When the PC receives a frame with a terminator, it sends the response.
• If there was more than one response frame, delimiters would be used
here too.
Frame 2 (command)
Text
FCS
Delimiter
Delimiter
R 0 0
Text
0100 0000
EOR
0011 0001
EOR
0011 0000
EOR
0101 0010
0011 0001
0100 0010
Converted to hexadecimal.
4 2 Handled as ASCII characters.
Frame 3 (command)
Terminator
Delimiter
Section 4-4
0 1 4 2
FCS Terminator
Text
FCS
@ Unit No.
Header code
End code
Text
FCS
Terminator
Frame (response)
47