3. Instruction Set
3-259
Sending data: (PLC→External equipment)
D100L D101L D102L D103L
Source data register, starting from
lower 8 bits of D100
Length = 4
Receving data: (External equipment→PLC)
D120L D122L D123L D124L D12
5L D126LD121L
Registers for r starting from
lower 8 bits of D120
eceived data,
Length = 7
Program Example 7: COM3 RS-485
Executing RS instruction with the newly added M1263, you can set the data receiving as
completed, when the data receiving stops for a period of time that is longer than what you have
set in D1168 (The specific end word to be detected for RS instruction to execute an interruption
request). Be sure to set the time in D1168 shorter than the time you set in D1129; otherwise, it
may be treated as communication timeout.
The flow of data receiving may NOT always be as regular or consistent. After receiving one
word of data, the PLC CPU starts to time to determine if the data receiving continues and when
the data receiving stops longer than the time set in D1168, the data receiving will be seen as
completed.
Example:
We can see there are two noticeable stops in this diagram.
The flow of data receiving stopped between data 33 and data 34. But since the stopped time is
less than what is set in D1168, the data 34 is treated as part of the data string and the data
receiving continues.
The flow of data receiving stopped between data 35 and data 36. Since the stopped time is
longer than what is set in D1168, the data 36 is NOT treated as part of the data string and the
data receiving stops after data 35 is received.
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