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10.4.2 User definition communication frame structure
Frame structure of PC Link, communication protocol of Han-Young used in this example, is as follows.
• Frame of temperature controller is executed as ASCII character string, it can read/write defined D, I
Register. There are two protocols, STD standard protocol and SUM protocol adding Check Sum to
standard type and protocol is selected by parameter of temperature controller. Standard protocol is
STD”. It starts with first character STX (0x02) and ends with last character CR(0x0D) LF(0x0A).
The following [Table 10.4.2] and [Table 10.4.3] indicates structure of standard protocol and Sum
protocol.
[Table 10.4.2] standard protocol structure
[Table 10.4.3] SUM protocol structure
(1) Writing example frame
In this example, present value and setting value is saved in M device area of PLC. [Table 10.4.4] is
frame requesting continuous data and [Table 10.4.5] is frame responding to request.
[Table 10.4.4] request frame
• DRS: command that request reading continuous D register value. No of data and start address of
D register is necessary.
• In the example, no. of data is 2 and start address is 01.
[Table 10.4.5] response frame
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