Need Help!

Can anyone please tell me which memory of a PLC decides Number of supported DI/O or AI/O.

I have S71200  CPU 1211 and 1212 (DC DC DC).

And how to calculate Expansion Modules to Input/Output.

For example:

Total expansion modules to total DIO.

Total expansion modules to total AI/O.

Hello Khanzada0786,

the number max of I/O per CPU in 1200 line are:

attached CPU specs compare

Hi Diniz,

Thanks for the response.

But my question still remains. Which type of memory decides total number of inputs and outputs?

1212C supports two expansion modules:

If i connect all DI/O modules.

OR

If i connect all AI/O modules.

Then i need total number of input/output calculation?

hi Khanzada,

no one of them.

It´s ment all together. The total number of Inputs and outputs is not depending on digital or analogue I/O´s.

The S7-1212 has an Address-area of 1 kbyte. That means addresses in the central and decentral periphery.

It doesn´t matter if your expansion-modules are analogue or digital.

hope this helps,

regards,

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---

BR

DINIZ

if it was helpful, please rate the post!

Hi,

Thanks for the response.

1Kb=8000 bit

So it mean that i can connect 8000  DI/O to CPU 1212C.

1Kb=1024 bytes

and 512 AI/O.Because one analog input or output uses 2 bytes.

But there is no such expansion module.Am I right?

regards,

Dear Khanzada0786,

The memory of CPU is used to storage the user program and to processing the operational system because it math is a little bit different.

those values what you mentioned are a high density of phisical I/O and for that quantity you probably need a S7-400 CPU...

—

BR

DINIZ

if it was helpful please rate this post.

Khanzada0786

Hi,

Thanks for the response.

1Kb=8000 bit

So it mean that i can connect 8000  DI/O to CPU 1212C.

1Kb=1024 bytes

and 512 AI/O.Because one analog input or output uses 2 bytes.

But there is no such expansion module.Am I right?

regards,

The allocation of the memory for the S7-1200 is fixed in size and type. The linking to IO comes with addressing space made available.

Regardless of this, Siemens has fixed the count of expansions that you can use. For all you have the 3 communication modules to the left and the expansion card that pushes onto the main CPU.

The expansions to the right of the CPU is fixed according to the PLC you choose. That is more to do with the power made available on the internal bus, but it is most to do with the limitation that Siemens put there.

The CPU1212 handles two cards to the right. Nothing more. You have to ensure you have the maximum density cards you can find as there is no way around the set rule of two cards.

Better news is that communication driven IO can be used. Even linking to another S7-1200 is made more-or-less easy. The less expensive way remains to get a CPU1214.

The communication linked devices make use of the extra addressing space which is not used by the extension cards. As you have mentioned, that is more than you can use for S7-1200 type projects.

Best you explain the root cause of your questions to give the helpers the opportunity to solve the real problem.

Thanks for the response.

The problem is that I have an S7-1200 CPU 1212C which allows only two expansion modules.

Now if I use two analog modules each containing 8 channels, which is the maximum number of channel currently available in a Siemens S71200 AIO expansion module.i.e (6ES7231-4HF32-0XB0).

This will give me a total AIO count  as follows,

From expansion modules: 16 channels

Built in : 2 channels

Signal board expansion :1 channel    i.e(6ES7231-4HA30-0XB0)

Total AIO=16+2+1=19 Channels

Is this configuration correct?

This arrangement will not have any negative effect on the processing power of the CPU?

regards,