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(2) Read (receive) data (slave to master)
(a) Command data are converted into ASCII code and transmitted.
(b) Comms byte quantity is 10.
(c) Comms data format (transmission sequence)
・STX (start code) : Code indicating start of text.
1 byte (02H)
・Text data : Transmit / receive data.
6 byte (ASCII code)
・ETX (end code) : Code indicating end of text.
1 byte (03H)
・SUM : XOR result (FFH), of adding STX, Text data, and ETX.
2 byte (ASCII code)
(d) Text data details (transmission sequence)
・Data (note) : Sets Read data to be transmitted.
2 byte x 3 (ASCII code)
Note: Data transfer sequence
Area address Data type Data bytes 1st byte 2nd byte 3rd byte
1 Data 0x00 0x00
Common data 2 Upper Lower 0x00
0x01 (Send data),
0x81 (Read command)
3 Upper Mid Lower
5. Calculation method of checksum
Example
1 2 3 4 5 6 7
STX
STATUS ID NO AREA ADDRESS RELATIVE NO DATA
ETX SUM
02 01 FF 01 04 00 00 00 03 28
1. STAUTUS to DATA are transformed into hexadecimal number on the basis of the ASCII code.
'0'→(30)
16
'1'→(31)
16
'4'→(34)
16
'F'→(46)
16
STX: (02)
16
ETX: (03)
16
2. STX to ETX are added all.
(02)
16
+(30)
16
+(31)
16
+(46)
16
+(46)
16
+(30)
16
+(31)
16
+(30)
16
+(34)
16
+(30)
16
+(30)
16
+(30)
16
+(30)
16
+(30)
16
+(30)
16
+(03)
16
＝(2D7)
16
STX STATUS ID AREA RELATIVE DATA ETX
3. The XOR (Exclusive OR) between the value obtained in 2 clause and (FF)
16
are taken, then two column under the
answer become SUM
(2D7)
16
XOR (FF)
16
= （228）
16
S T X
1 byte
Text data
6 byte
E T X
1 byte
S U M
2 byte
10 byte
Data
2 byte x 3
6 b
y
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