Help PLZ, confused in Data Comparison

[ahsen001]

Thanx LD. Thanx alot...!

I have simulated your code, it is working properly. But i am confused in some of your STL text that why have you written these. For example in FC1, why u have written first nine lines.

Can you write comment in front of these. I mean purpose of each line....? Remaining program i have got completely. But only these lines are confusing.

 

[L D[AR2P#0.0]]

Added.

 

[ahsen001]

OK.

It means you have used DB POINTERS. DB Pointer contains both the DATA BLOCK NUMBER and DATA ELEMENT ADDRESS.

DATA BLOCK NUMBER is a 16-bit Integer Value.
DATA ELEMENT ADDRESS is a 32-bit AREA CROSSING POINTER.

U have initially wrote this command:

L P##pLookUp

// pLookUp is a local input Variable And you have assigned this value DB1.DBX0.0

LAR1

// Load the value (DB1.DBX0.0) in Address Register-1

L W[AR1, P#0.0]

// This instruction means that LOAD the Accumulator with the contents of Marker Word addressed by the sum of AR1 and the Offset P#0.0.
Then how to get the DB number from the above instruction............?

T #iDB
// Transfer the DB number for next time opening the DB......it is OK.

L D [AR1, P#2.0]

// Also how this instruction get area pointer by summing AR1 & P#2.0........?
Plz explain more about these two instruction.

 

[L D[AR2P#0.0]]

All FC parameters are 32 bit area pointers. As a DB pointer is larger than this, the DB pointer is stored in the local data of the calling block and the actual parameter passed is a pointer to the local data area of the calling block.

Have a look at the following:

http://www.plctalk.net/qanda/showthread.php?t=54702&highlight=fc+parameters