Azbil F4Q, Руководство пользователя

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4-9
Chapter 4. CPL Communication
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Ex.: “0123” (30H, 31H, 32H, 33H) is not allowed.

Ex.: “ 123” (20H, 31H, 32H, 33H) is not allowed.
•
If the number is 0, one "0" is used.

Ex.: “0” (30H).
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Ex.: “00” (30H, 30H) is not allowed.
•
Negative numbers are preceded by a minus sign (2DH).

Ex.: “−123" (2DH, 31H, 32H, 33H)
•
Positive numbers are not preceded by a plus sign.

Ex.: “+123” (2BH, 31H, 32H, 33H) is not allowed.
„ RD command (hexadecimal format consecutive data read)
z RD command instruction message
This is a command—in one message—to read fixed-length data from consecutive
data addresses starting from the specified address in hexadecimal format.
This command is suitable for handling data in ladder programs sent by PLC
communications as the data is of a fixed length.
Read instruction code
Read start data address
Read count
02H 30H 31H 30H 30H 58H 52H 44H 30H 33H 45H 39H 30H 30H 30H 32H 03H 41H 39H 0DH 0AH
STX 0 1 0 0 X R D 0 3 E 9 0 0 0 2 ETX A 9 CR LF
Data link layer Application layer Data link layer
• Use capital letters in character codes for all numbers and characters in the
application layer.
• Each value is expressed as a four-digit hexadecimal number.
• Since the data length is fixed, commas are not used to delimit the data.
• The above figure shows how a single message instructs the reading of two pieces
of data (starting from address "03E9").
1. Read instruction code (RD)

Role : This is the command for reading fixed-length data in hexadecimal
format.

Description : Two characters, "RD" (52H, 44H).