Bit Memory adressing limit for Siemens CPU

userxyz · Apr 19, 2011

How can I know the bit memory adressing limit of a CPU ?

I have this CPU: 6ES7 314-6CG03-0AB0

M600.0 gives errors, not in PLCSim, only when downloading. When I change the adress to M100.0, no errors.

I googled for the resources of such CPU. But didn't find anything specifically about the adress limit...

Anyone know where to find this ?

Thanks,

Kind regards,
Combo

TurpoUrpo · Apr 19, 2011

It is in manual.

For example, CPU314:

Data areas and their retentivity
Bit memory
Number, max. 256 bytes
Retentivity, available Yes (MB 0 to MB 255)
Retentivity, default MB0 to MB15
Clock memories 8 (1 memory byte)

sudheendra.r · Apr 19, 2011

it is given in the manual of the CPU or you can find it online in "Module information" of the CPU. No of Inputs, Outputs, Bit memory, DB memory timers/counters etc..

userxyz · Apr 20, 2011

Ok

I found 256 MByte's for the 314.
But, adress M300.0 is accepted ?

sudheendra.r said:
it is given in the manual of the CPU or you can find it online in "Module information" of the CPU. No of Inputs, Outputs, Bit memory, DB memory timers/counters etc..

TurpoUrpo · Apr 20, 2011

Combo said:
I found 256 MByte's for the 314.
But, adress M300.0 is accepted ?

Look at the manual I linked. Look at different CPU specs. Look at the amount of M memory each has. Now, think how could editor not accept m300.0.

userxyz · Apr 20, 2011

hmm

M300.0 is accepted !! That's what I don't understand !!

TurpoUrpo said:
Look at the manual I linked. Look at different CPU specs. Look at the amount of M memory each has. Now, think how could editor not accept m300.0.

L D[AR2P#0.0] · Apr 20, 2011

The editor does not check which CPU you are using. It is only when you attempt to download to the CPU that you will discover if any addressing is out of range for that CPU.

JRW · Apr 20, 2011

Hit ctrl d and look at address limit there
this is the online limits for that cpu

userxyz · Apr 20, 2011

Thanks

Module information...
Thanks, I'll check it out with an online connection tommorow.

JRW said:
Hit ctrl d and look at address limit there
this is the online limits for that cpu

TurpoUrpo · Apr 20, 2011

Combo said:
Module information...
Thanks, I'll check it out with an online connection tommorow.

Did you even open up the manual? For example CPU315-2DP has 2048 bytes of m area. Ofc editor must accept values like m300.0. Its the compiling state when you make the download that checks compability.

Imho, m area should be avoided when writing program.

L D[AR2P#0.0] · Apr 20, 2011

Why ?

userxyz · Apr 20, 2011

ok

Yes I did. 314 has 256 byte's and 313 128 byte's.
But offcourse, DB's are retentive by default in simatic manager, m area is for testing. A collegue of me used the PLCSim and M600.0. This worked, but not in his CPU. When he changed it to M300.0 he could download and it worked...

TurpoUrpo said:
Did you even open up the manual? For example CPU315-2DP has 2048 bytes of m area. Ofc editor must accept values like m300.0. Its the compiling state when you make the download that checks compability.

Imho, m area should be avoided when writing program.

TurpoUrpo · Apr 20, 2011

L D[AR2 said:
Why ?

I think DB's are easier to maintain and can be used with more describing symbols and structure. As with all, its not black and white never use m area, its more like use it only when really needed. Testing is one good use of it.

So back at you, why you would use m area over db?

TurpoUrpo · Apr 20, 2011

Combo said:
Yes I did. 314 has 256 byte's and 313 128 byte's.
But offcourse, DB's are retentive by default in simatic manager, m area is for testing. A collegue of me used the PLCSim and M600.0. This worked, but not in his CPU. When he changed it to M300.0 he could download and it worked...

Yeah, plcsim sucks for many things. Never assume it works like real plc

for example some instructions clear accu2 when executed in plcsim but work like documented in real plc (ofc).

L D[AR2P#0.0] · Apr 20, 2011

Less execution time, smaller program, does not modify currently open DB, common use between s5/s7

Bit Memory adressing limit for Siemens CPU

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