10
6
Data
: The contents of data differ depending on the reading command.
Composed of hexadecimal 4 digits (See pages 13 to 20.)
7
Checksum
: 2-character data to detect communication errors (See page 10 for the calculation.)
8
Delimiter
: ETX (03H) fixed, End of text
Control code to represent the end of response
Acknowledgement
1
Header
: ACK (06H) fixed, [Acknowledgement]
Control code to represent the beginning of the response
2
Address
: Instrument number 0 to 95 (20H to 7FH) to which the response is transmitted.
The same code with the received command is used for the response.
3
Checksum
: 2-character data to detect communication errors (See page 10 for the calculation.)
4
Delimiter
: ETX (03H) fixed, End of text
Control code to represent the end of response
Negative acknowledgement
1
Header
: NAK (06H) fixed, [Negative acknowledgement]
Control code to represent the beginning of the response
2
Address
: Instrument number 0 to 95 (20H to 7FH) to which the response is transmitted.
The same code with the received command is used for the response.
3
Error code
: Represents an error type. Composed of hexadecimal 1 digit.
1 (31H)-----Non-existent command
2 (32H)-----Not used
3 (33H)-----Setting value outside the setting range
4 (34H)-----Status unable to set (e.g. AT is performing)
5 (35H)-----During setting mode by keypad operation
4
Checksum
: 2-character data to detect communication errors (See page 10 for the calculation.)
5
Delimiter
: ETX (03H), fixed, End of text
Control code to represent the end of response
5.2 Checksum calculation
Checksum is used to detect receiving errors in the command or data.
Set the program for the master side as well to calculate the checksum of the response
data from the slaves so that the communication errors can be checked.
The ASCII code (hexadecimal) corresponding to the characters which range from the address
to that before the checksum is converted to binary notation, and the total value is calculated.
The lower 2-digits of the total value are converted to 2’s complements and then to hexadecimal
figures, that is, ASCII code for the checksum.
Checksum calculation example
Main setting value: 600 (Fixed value control)
Address (instrument number): 0 (20H)
• 1’s complement: Reverse each binary bit. 0 will become 1 and vice versa.
• 2’s complement: Add 1 to 1’s complement.
Address
Header
1
2
Checksum Delimiter
3
4
Address
Header
1
2
Checksum Delimiter
3
4
Error
code
5
