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

Extended instructions
8.2 String and character
RET_VAL Description
(W#16#....)
8101 Illegal or invalid input pointer, for example, an access to a DB that does not exist.
8120 Input string is an invalid format, i.e., max= 0, max=255, current>max, or grant length in
pointer < max
8182 Input buffer is too small for N
8151 Data type not allowed for input buffer
8301 Illegal or invalid output pointer, for example, an access to a DB that does not exist.
8320 Output string is an invalid format, i.e., max= 0, max=255, current>max, or grant length
in pointer < max
8382 Output buffer is too small for N
8351 Data type not allowed for output buffer
8.2.4

String operation instructions

Your control program can use the following string and character instructions to create
messages for operator display and process logs.
8.2.4.1

MAX_LEN (Maximum length of a character string) instruction

Table 8- 47 Maximum length instruction
LAD / FBD SCL
out :=
MAX_LEN(in);
Table 8- 48 Data types for the parameters
Parameter and type
IN IN
OUT OUT
306
Description
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
length.
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.
Data type
String
DInt
Description
Input string
Maximum number of characters allowed for IN
string
S7-1200 Programmable controller
System Manual, 03/2014, A5E02486680-AG
ENO
FALSE
FALSE
FALSE
FALSE
FALSE
FALSE
FALSE
FALSE