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8-4-2. ASCII mode message
Calculate error check LRC from message basic division. LRC becomes 7BH (See section
8-3-5.②).Convert each data of basic division to ASCII code and also convert LRC to ASCII code and
add it to basic division. Starting character of message is ":" and add "CR", "LF" at the end.
［３ＡＨ］［３０Ｈ］［３２Ｈ］［３０Ｈ］［３４Ｈ］［３０Ｈ］［３０Ｈ］［３７Ｈ］［４４Ｈ］
［３０Ｈ］［３０Ｈ］［３０Ｈ］［３２Ｈ］［３７Ｈ］［４２Ｈ］［０ＤＨ］［０ＡＨ］
8-5. Function code
Function code wise response is shown below. (See section 8-3-2 <Table 2. Function code table>)
Note) See section 8-6 for response in case of abnormality
8-5-1. Reading digital input data [Function code: 02 (02H)]
From the specified numbers, only the number of units that are specified 'Digital (ON/OFF) input
data with continuous numbers' are read. ON/OFF data is made up of response message data in
which 8 units are arranged in numeric order for 1 data (1 byte). LSB (DO side) of each data becomes
a digital data of the smallest number. If the units that are to be read are not in multiples of 8, then the
bits that are not required become 0.
Example) Reading the digital settings value reference number 10005 of slave 1
Reference number 10005
Data 0
System normal
<RTU mode>
Master → Device
Device → Master (Normal)
Slave address 01H
Slave address 01H
Function code 02H
Function code
02H
Starting number (H) 00H
Data count 01H
Starting number (L) 04H
Initial 8 data 00H
Number of units (H) 00H
CRC(L) A1H
Number of units (L) 01H
CRC(H) 88H
CRC(L) F8H
CRC(H) 0BH
LRC F8H
LRC FCH
Note) Starting number (Relative number) is 'Reference number - 10001'.
(Decimal 10005 (=10005 - 10001) → Hexadecimal 04H)
Note) Data count is the number of bytes of data.
(It differs from request units. In the example request unit is 1 unit, data count is 1 unit).
７ＤＨ
００Ｈ
０４Ｈ０２Ｈ
［：］
ＬＦ
ＣＲ
７ＢＨ
ＬＲＣ
０２Ｈ ００Ｈ
<ASCII mode error check> (*CRC(L)(H) of the above are LRC as follows.)
0 0 0 0 0 0 0 0
First 8 data
108 101
Reference number
(00H)
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