Omron CQM1H-SCB41 operation manual Communications Sequence, Computer

Application Procedure Section 4-4

Communications Sequence

that is included in the frame makes it possible to check for data errors in the frame.

@	1	0	R	R	0	0		0	1	4		2		↵
	Node No.		Header code				Text				FCS		Terminator
			FCS calculation range
		ASCII code
@		40		0100	0000
				EOR
1		31		0011	0001
				EOR
0		30		0011	0000
				EOR
R		52		0101	0010
1		31		0011	0001
Calculation				0100	0010
				↓	↓	Converted to hexadecimal.
result
				4	2	Handled as ASCII characters.

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 trans- mission right is traded back and forth between the host computer and the PC each time a frame is transmitted. An example sequence for multiframe commu- nications between the host computer and PC is described below. Multiframe communications are handled by exchanging delimiters and then using termina- tors 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 terminator 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 1 (command)

	@ Unit No.
	Header code
Host	Text
computer
	FCS
	Delimiter
PC		Delimiter

Frame 2 (command)

Text

FCS

Delimiter

Delimiter

Frame 3 (command)

Text

FCS

Terminator

@ Unit No.

Header code

End code

Text

FCS

Terminator

Frame (response)

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