40
4. Operation Method
RS485 Communication Function
4.2 Message Types
■
Message types include transmission request messages from the host computer and
transmission reply messages from this unit.
■
All codes from STY, address, request, identifier to ETX (except BCC) are represented by ASCII
codes.
4.3 Request Message Structures (transmission from the host computer to the unit)
4.3.1 Structure of Read Request Messages
S
T
X
□
□
R
□
□
□
E
T
X
B
C
C
① ② ③ ④ ⑥ ⑦
4.3.2 Structure of Write Request Messages
S
T
X
□
□
W
□
□
□
□
□
□
□
□
E
T
X
B
C
C
① ② ③ ④ ⑤ ⑥ ⑦
4.3.3 Structure of Storage Request Messages
S
T
X
□
□
W
S
T
R
E
T
X
B
C
C
① ② ③ ④ ⑥ ⑦
①
Start code
②
Address
③
Request (read)
④
Identifier
⑤
-
⑥
End code
⑦
BCC data
①
Start code
②
Address
③
Request (write)
④
Identifier
⑤
Numeric data
⑥
End code
⑦
BCC data
①
Start code
②
Address
③
Request (write)
④
Identifier
⑤
-
⑥
End code
⑦
BCC data