MEMCMP

MEMCMP 1:

The function MEMCMP allows the values of PLC variables in two different memory areas to be compared.

FUNCTION MEMCMP : INT

VAR_INPUT

pBuf1     :DWORD;
pBuf2     :DWORD;
n         :UINT;

pBuf1: start address of the first memory area (the first data buffer).

pBuf2: start address of the second memory area (the second data buffer).

n: number of bytes to be compared.

The function compares the first n bytes in the two data buffers and returns a value that corresponds to their relationship.

Return parameter	Relationship of the first byte that differs between the first and second data buffers
-1	pBuf1 smaller than pBuf2
0	pBuf1 identical to pBuf2
1	pBuf1 greater than pBuf2
0xFF	Incorrect parameter values. pBuff1 = 0 or pBuff2 = 0 or n = 0

Sample of a call in FBD

VAR
    Buffer1    : ARRAY[0..3] OF BYTE;
    Buffer2    : ARRAY[0..3] OF BYTE;
    CmpResult  : INT;
END_VAR

MEMCMP 2:

In this sample, 4 bytes of data in Buffer2 are compared with those in Buffer1. The first differing byte is larger in Buffer1 than it is in Buffer2.