String Operation Instructions; Max_Len (Maximum Length Of A Character String) Instruction - Siemens S7-1200 System Manual

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Table of Contents

Extended instructions

8.2 String and character

Illegal or invalid input pointer, for example, an access to a DB that does not exist.

Input string is an invalid format, i.e., max= 0, max=255, current>max, or grant length in

pointer < max

Input buffer is too small for N

Data type not allowed for input buffer

Illegal or invalid output pointer, for example, an access to a DB that does not exist.

Output string is an invalid format, i.e., max= 0, max=255, current>max, or grant length

in pointer < max

Output buffer is too small for N

Data type not allowed for output buffer

String operation instructions

Your control program can use the following string and character instructions to create

messages for operator display and process logs.

Maximum length instruction

MAX_LEN(in);

Data types for the parameters

Parameter and type

MAX_LEN (Maximum length of string) provides the maximum length value

assigned to string IN at output OUT. If errors occur during processing of the

instruction, then an empty string length will be output.

The STRING data type contains two lengths: the first byte gives the maximum

length and the second byte gives the current length (this is the current number

of valid characters).

The maximum length of the character string is assigned for each STRING

definition in square brackets. The number of bytes occupied by a string is 2

bytes greater than the maximum length.

The current length represents the number of the character places actually

used. The current length must be less than or equal to the maximum

Use the MAX_LEN instruction to get the maximum length of the character

string and the LEN instruction to get the current length of a string.

Input string

Maximum number of characters allowed for IN

S7-1200 Programmable controller

System Manual, 03/2014, A5E02486680-AG