STL pointers problem

AmirAlwaled

I was reading pdf :" Pointers and Indirect addressing in S7 PLCs, volume 1- Memory Indirect addressing " ,

and when I tried this code :
L MB [MD4]
it works but when I tried this code :
L B [MD4]
it didn't !
why ?

algudkar

AmirAlwaled

I was reading pdf :" Pointers and Indirect addressing in S7 PLCs, volume 1- Memory Indirect addressing " ,

and when I tried this code :
L MB [MD4]
it works but when I tried this code :
L B [MD4]
it didn't !
why ?

Hi amir
First on is in your program code is Loading the Memory Byte MD 4 its long double or double word in llength. but M yor trying to load its asking whether its byte word long double integer..so only m YOU cnt load

regards
algudkar

AmirAlwaled

I was reading pdf :" Pointers and Indirect addressing in S7 PLCs, volume 1- Memory Indirect addressing " ,

and when I tried this code :
L MB [MD4]
it works but when I tried this code :
L B [MD4]
it didn't !
why ?

dchartier

Hello Amir;
The code L MB___ refers to an instruction code(L = load) and a valid address format (MB = M memory area, Byte value); the [MD4] part will be replaced at runtime by the contents of MD4,
So, it has correct syntax for the system to recognize it as a valid instruction.

The code L B[MD4] will not be recognized as valid because it lacks the memory area designation.

Hope this helps,
Daniel Chartier

• Memory area in the CPU (the following table shows the hexadecimal codes of the memory areas for the parameter type POINTER)

SolutionFinder

Dear AmirAlwaled,
Also you need to note down that if you are using any Double Int as indirect addressing then it must be multiple of eight with the actual address you want.
So if you want to load value at address MD 400 then you mast use below instruction:
L MB [MD 4]
Where value inside the MD 4 must be 400* 8. So it would be 1600.

playerslight

It can't be B[md4} it if you want to use a memory merker you need to use mb{md4} not the b by itself