KW8M Eco-POWER METER (1A/5ACT input type)
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7.3 MEWTOCOL Communication
7.3.1 Overview of MEWTOCOL-COM (RS485)
◆
Command and response functions
The computer sends commands (instructions) to Eco-POWER METER, and receives responses in
return. This enables the computer and Eco-POWER METER to converse with each other, so that
various kinds of information can be obtained and provided.
①
Commands
Computer
Eco-POWER
METER
②
Responses
◆
Command and response formats
Command message
(Host computer) Header
Des-
tination
Text
Check
code
Termi-
nator
(To next command)
(Eco-POWER METER)
Header
Source
Text
Check
code
Termi-
nator
Normal response message
◇
Control codes
Name Character
ASCII
code
Explanation
Header
%
25H
Indicates the beginning of a message.
Command
#
23H
Indicates that the data comprises a command
message.
Normal
response
$
24H
Indicates that the data comprises a normal response
message.
Error
response
!
21H
Indicates that the data comprises a response message
when an error occurs.
Terminator
CR
0DH
Indicates the end of a message.
◇
Destination and source AD (H), (L)
Two-digit decimal 01 to 99 (ASCII codes)
Command messages contain a station number for Eco-POWER METER that receives the message.
When FF (ASCII code table) is used, however, the transmission is a global transmission (sent to all
stations at once).
Note) When a global transmission is sent, no response to the command message is returned.
◇
Block check code Bcc (H), (L)
Two- digit hexadecimal 00 to FF (ASCII codes)
These are codes (horizontal parity) that are used to detect errors in the transmitted data.
If “
**
” is entered instead of “Bcc”, however, messages can be transmitted without the Bcc. In this case,
the Bcc is included with the response
◇
Error code Err (H), (L)
Two- digit hexadecimal 00 to FF (ASCII codes)
These indicate the content if an error occurs.
◆
Bcc
(
Block Check Code
)
-The Bcc is a code that carries out an error check using horizontal parity, to improve the reliability of
the data being sent.
-The Bcc uses an exclusive OR from the header (%) to the final character of the text, and converts the
8- bit data into a 2-character ASCII code.
Example)
%
0 1
#
R T
0 1 CR
↑
↑
↑
↑
↑
Header
Station
No.1
Command
RT
Command
2-character
Bcc
%
0
1
#
R
T
0 1
25H
30H
31H 23H 52H
54H
Bcc(H)=0(30H)
Bcc(L)=1(31H)
①
Takes exclusive OR
②
Converts to ASCII format