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HTTP server functions/web pages
Further examples:
12.1.12.2
Notes on strings
N o t e
106
More PLC data entry examples can be found in "Example - Web pages and
e-mail".
The format definition S is used for ASCII strings without "header", i.e. an ASCII
string is generated with the F95 command in the PLC. The length that was
determined in the input field definition is the maximum string length that can
be transferred to the PLC. It can be shortened even further with the format
command .xS. In this case x stands for the number of characters of the
shortened string length.
– NULL-String: If such a string has the length 0 (zero) the data in the PLC is
not changed.
The format definition s is used for ASCII strings with "header", i.e. ASCII
strings that have been generated with the string commands of FPWIN Pro
(from version 3.0 on) in the PLC. The "header" consists of two 16-bit words
before the real ASCII string.
– 1st Word: Maximum string length permitted that can be saved here. Zero
disables writing.
– 2nd Word: Current length of the strings.
– 3rd Word and following: ASCII characters of the string in LO/ HI sequence
in the word.
– Firstly, the entered string will always be shortened to the length that is
depicted in the SIZE="x" command. Secondly, this string can be shortened
even further with the format command .xs. Thirdly, the maximum memory
permitted (Header 1st Word) has to be taken into account. After the
transmission of the string to the PLC, the "header" (2nd Word) with the new
length will be updated.
– Un-initialized String: If a string variable is not initialized by the FPWIN
Pro project, the 1st Word (maximum string length) is zero. With this the FP
Web-Server cannot store any character in this string because no memory is
reserved for storing!
– Null-String: If such a string has the length 0 (zero) the current length of
the string (2nd Word) is also set to 0, i.e. the string is deleted.
A string (s or S) of an input field (determined by MEWTOCOL) can only be 48
characters long! Compare to display fields for strings that are 52 characters
long!
The special characters < and > are transcribed as ¼ and ¾ characters when
the strings are displayed. If the special characters ¼ and ¾ are used in input
fields, they will be transcribed into the characters < and > before they are
transmitted to the PLC.
Only 7-bit ASCII characters (see p. 115) are supported when strings are
displayed or entered in HTML.
FP Web-Server V2.810 EN
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