15
(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 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
0x01 (Send data),
0x81 (Read command)
1
Data
0x00
0x00
Common data
2
Upper
Lower
0x00
3
Upper
Mid
Lower
5. Calculation method of checksum
Example
STX
1
2
3
4
5
6
7
ETX
SUM
STATUS
ID NO AREA ADDRESS RELATIVE NO
DATA
02
01
FF
01
04
00
00
00
03
28
i. 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
ii. 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
iii. The XOR (Exclusive OR) between the value obtained in ii. 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 byte
