External control

■Commands and responses

・Instructions sent to the controller are called commands.

・Messages returned from the controller are called responses.

・The communications are two-way. (When a command is sent, a response is always returned.)

・Data is sent in ASCII format.

Warning

・When a response is not received, this indicates that the transmission format is wrong, the command has not yet reached its destination, or the controller is not in operation. Check the communication specifications, such as the transmission speed, data lengths, and parity.

・When a response with “!” instead of “$” stored is r eceived, it indicates that the command has not been processed correctly. Check the communication error code stored in the response to identify the error.

■Command/response format

Command message

■Block check code BCC (H) (L)

Binary hexadecimal 00-FF (ASCII-encoded)

・To improve the reliability of transmission data, this encoding enables error detection using longitudinal parity bits. However, if “**” appears instead of BCCs, transm ission is possible without BCCs. Even in this case, however, BCCs will be included in the response.

・BCCs are created by taking the exclusive OR from the header (<) to the final character of the text, and then encoding this 8-bit word into a 2-character ASCII code.

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