401
3)Limit the number of reading and writing data of word
A piece of data cannot be read only part of it. For example, the format is defined as W, DW,
S8. If you read from the first column W and the number of words read is 10, S8 cannot be
read completely, and the program will report an error (the correct number of words is 3, or
11). When the program judges that the parameters are wrong, it will not read or write the SD
car.
4) Create CSV file restrictions
if you use the notepad provided by Windows to create a CSV file, the end of the last
line must be wrapped, and the data is created strictly according to the type definition
(table in section 10-5-1), as shown in the following figure:
existing CSV files can only be used after being converted by using the format
conversion tool in section 10-5-5.
5) Limit in read and write
In the read instruction, if the specified number of lines exceeds the actual number of lines in
the file, the program will report an error.
6) Write process description
In the write instruction, if the specified number of lines exceeds the actual number of lines of
the file, the file will be extended. During the expansion process, insert spaces in the
corresponding positions according to the column data type, leaving a fixed space for inserting
data later.
Notes:
If the number of lines written is greater than the actual number of lines in the file, the file will
be expanded. The file expansion speed is very slow, which will affect the PLC scanning cycle
and cause the watchdog to trigger. This is not recommended.
7) SD card status information
The status information of the SD card can be viewed through the special register SD453, as
shown in the following table:
Read/write files does not exist
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