Energy Meter Manual

4-3

IM 77C01E01-10E

(8) ETX (End of Text)

This control code indicates the end of a command string. The ASCII code is 03 in

hexadecimal.

(9) CR (Carriage Return)

This control code indicates the end of a command. The ASCII code is 0D in hexadeci-

mal.

NOTE

The control codes “STX”, “ETX”, and “CR” are essential for commands when you create a

communication program for PC link communication. Omission of any of them or incorrect

order of them results in communication failure.

4.1.2 Configuration of Response

Responses from the PR300 with respect to a command sent from the higher-level device

consist of the elements shown below, which differ depending on the condition of communi-

cation; normal or failure.

1) Normal Communication

When communication completes normally, the PR300 returns a character string “OK” and

data corresponding to a command.

No parameter data area for write command.

Number

of Bytes

Variable length12 22 211

Element STX Station

number

(ST-NO)

CPU

number

OK Parameter data Checksum ETX CR

2) In the Event of Failure

If communication does not complete normally, the PR300 returns a character string “ER”

and error code (EC1 and EC2). (See subsection 4.1.3, “Response Error Codes”.)

• No response is made in case of an error in station number specification or CPU

number specification.

• If a PR300 cannot receive ETX in a command, response may not be made.

Note: As a countermeasure, provide a timeout process in the communication functions of the higher-level device or in

communication programs.

Number

of Bytes

12 22223 211

Element STX ER EC1 EC2 Command Checksum ETX CRStation

number

(ST-NO)

CPU

number