Siemens S5 to S7 help

[PLCKeef]

Hi all
I need some help to move from s5 to s7 programming.
Here is an S5 program that I need to know how to do in s7.

Lets say I have a 4 digit thumbwheel switch at IW124 and I want to use the right hand digit to specify where the left three digits are transferred to.

e.g
FB1
LIW124
LKH000F
AW
TFW20;right hand digit on it's own

LIW124
LKHFFF0
AW
SRW4
TFW22;left hand digits on their own

LFW22
DO FW20
TDWO;transfer FW22 to the data word specified by FW20


I am having trouble with doing the last part in s7 I can't work out how to make the pointer variable under S7 ?
LFW22
DO FW20
TDWO

Any help would be great.

 

[SimonGoldsworthy]

Here is my code snippet. Note that in Step7 the addressing scheme refers to bits, hence to find a word number you need to shift left 4 bits.

	  L	 MW	20	 //get Step 5 dw number
	  SLD   4			//convert to Step 7 dbw
	  LAR1			   //address register allows indirect access
	  T	 DBW [AR1,P#0.0] //then finally transfer

 

[Amr Hassan]

did u try to convert the block using the converter that comes with the s7 simatic manager?

 

[RolfB]

Hi,

I guess there is a little typo in Simons post.
Instead of 'SLD 4' write 'SLD 3' .Then it will
work correctly.
( the lowest 3 bits refers to the bit-adress 0-7 )


cheers

Rolf

 

[RMA]

Not this time, Rolf, he's working with WORDs. "SLD3" delivers the Byte address.

 

[RolfB]

oops,

absolutley right, thanks for correction.

cheers
Rolf

 

[PLCKeef]

OK thanks
I will give it a go today.
Not sure what LAR1 does , but I'll look it up.

 

[ivo.maenen]

LAR1 loads address register AR1 with the contents of ACCU 1 (32-bit pointer). ACCU 1 and ACCU 2 remain unchanged. The instruction is executed without regard to, and without affecting, the status bits.