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App6-24
Appendix 6 Universal Serial Communications
Data Items for Protocols
• Transmission control code
The transmission control codes are shown in the table below.
Signal Name
Code (Hexadecimal)
STX
02H
Contents
Start of transmission block
ETX
03H
End of transmission block
ENQ
05H
Interrupt
ACK
06H
Positive acknowledge
CR
0DH
Carriage return
DLE
10H
Change contents within a block
NAK
15H
Negative acknowledge
LF
0AH
Line feed
• Port number
Port numbers are used so that the host computer can identify each V series for access. The data
range is from 00H to 1FH (0 to 31) and is converted into two-digit ASCII code (HEX) before use.
The port number of the V series should be set on the V-SFT editor.
• Sum check code (SUM)
Data is added up (SUM), and the lower one byte (8 bits) of the sum is converted into the 2-digit
ASCII code (hexadecimal). A sum check code is shown below.
Example:
STX
Sum check will be as is shown below when data is transmitted as: command [WM]
(data writing), address [05AD] (1453), and memory data [OF2A] (3882) in
transmission mode [w/o CR/LF, w/ sum check].
Command
DLE
"W" "M"
02H
57H 4DH
10H
Address
Count
Memory data
"0" "5" "A" "D"
"0" "0" "0" "1"
"0" "F" "2" "A"
30H 35H 41H 44H
30H 30H 30H 31H
30H 46H 32H 41H
ETX
SUM
"4" "D"
03H
34H 44H
02H + 57H + 4DH + 10H + 30H + 35H + 41H + 44H + 30H + 30H + 30H + 31H
+ 30H + 46H + 32H + 41H + 03H = 4DH
However, in the case of an interrupt, data from ENQ to ETX is subject to a sum check.
• Error code
An error code is sent along with an NAK response.
An error code is transmitted as a two-digit ASCII code (HEX). For more information, refer to page
App6-37.