7-4
Chapter 7. CPL Communication Function
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List of data link layer data definitions
The following list shows the definitions for data in the data link layer.
Data name Character code Number of
characters
Meaning of data
STX 02 h 1 Start of message
Station address 0 to 7FH are expressed as
hexadecimal character codes.
2 Identification
of device to
communicate with
Sub-address 00 (30H, 30H) 2 No function
Device ID code X (58H) or x (78H) 1 Device type
ETX 03H 1 End position of the
application layer
Checksum 00H to FFH are expressed as
2-digit hexadecimal character
codes.
2 Checksum of
message
Delimiter CR (0DH), LF (0AH) 2 End of message
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Description of data items
• STX (02H)
When STX is received, this device interprets it as the start of a command
message. No matter what has been received previously, upon receiving STX, this
device begins processing a new message. In this way, if an instruction message
contains an error due to electromagnetic noise, etc., this device can respond to
the next proper message (a resent message, etc.) from the master station.
• Station address
This device creates a response message only to instruction messages that mention
its station address. A station address is expressed as a 2-digit hexadecimal
character code in a message.
This device returns a response message that includes its own station address. The
station address can be specified by C65 (station address). Note that, if the station
address is set to 0 (30H 30H), this device does not respond even if the station
addresses match.
• Sub-address
Set the sub-address to 00 (30H 30H), because this device does not use sub-
addresses.
However, this device will return a response message that includes a received sub-
address.
• Device ID code
X (58H) or x (78H) can be used. This code is determined for each product series,
and other codes cannot be selected. This device returns a response message that
includes the received device ID code. X (58H) is used as the default, and x (78H)
is used to distinguish the message from the resend message.
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