indirect addressing - fill memory function

I am trying to write a function that fills a memory, for example from byte no. 6 write 100 bytes using certain pattern:
IN value: start address [INT]
byte_count (how many bytes to write) [INT]
byte_pattern (e.g. B#16#FF) [BYTE]
It would help me to understand indirect addressing
thanks

Which plc/cpu? If using Step7 300/400 series, there is a system function that will do this. Do you want to do this "long hand" though to gain familiarity with indirect addressing ?

If its step 7 (300 or 400) there is a Fill function available

s7-300/CPU315 I was going to write such a block but not succeed ://

Library SFC21 FILL MOVE.

example


That move hex ff into marker byte 1, then fills DB5.dbb0 to db5.dbb499 with the hex value.

kyoq said:

I was going to write such a block but not succeed ://

Click to expand...

Do you want to post your block (post the source code as text) to find out why it did not work or are you going to use SFC21 ?

PeterW said:

example

Code:

	L	 W#16#FF
	T	 MB	 1
	CALL "FILL"
	 BVAL :=P#M 0.0 BYTE 1
	 RET_VAL:=MW2
	 BLK	:=P#DB5.DBX0.0 BYTE 500

That move hex ff into marker byte 1, then fills DB5.dbb0 to db5.dbb499 with the hex value.

Click to expand...

Just to streamline it a little bit, you really don't have to use the pointer format in this case for BVAL. Just type in MB1, and it will work the same way. I use "SFC Fill" to clear DBs all the time, and I just load a "0" in a temp int variable, enter it for BVAL, and it works fine.

Here is a fill function that does not use SFC21. Note that there is no error checking so if the db doesn't exist or is too small a CPU error will be generated.

Thanks for source, I modified this to fill memory:

FUNCTION FC 70 : VOID
TITLE =
VERSION : 0.1


VAR_INPUT
start_address : INT ; //Initial address
byte_count : INT ; //Ammount of bytes to be write
byte_pattern : BYTE ; //Byte pattern
END_VAR
VAR_TEMP
pointr : INT ;
END_VAR
BEGIN
NETWORK
TITLE =

L #start_address;
L 0;
==I ;
BEC ;
//*
L #start_address;
SLD 3;
LAR1 ;
L #byte_pattern;
L #byte_count;
P: TAK ;
T MB [AR1,P#0.0];
+AR1 P#1.0;
TAK ;
LOOP P;

END_FUNCTION

for inputs:
// CALL FC 70
// start_address:=8
// byte_count :=0
// byte_pattern :=B#16#F

I got an error Event 2x23 ...why ??

A byte count of zero will actually loop 65535 times and you will run off the end of the M area. Did you mean to check for a zero byte count instead of a zero start address ?

exactly ...fck :/// i missed this bug. THX !