Why analog input starting address 0 is not recommended

There are two method for IO addressing:
1. Slot Oriented 2. User Oriented
If your CPU support user oriented, you can change starting address to any number (This number must be less than address area). But It's not the whole story.
This is my personal experience:
If you change starting address of DI cards to a number bigger than starting address of AI cards, you can't access to data of that DI card.

I don't know why it happens. I'm sure there are a text or document in Siemens, but I can't found it.

So, for digital cards set start address for example from 0 and with a acceptable empty address, set start address for analog cards and in the future if you want to add digital cards you can change that starting address to a number in empty area.

Also, It's better to set size of process image input area in HW Config.
The result of this setting is acceleration in PII update time.

MRG

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If you change starting address of DI cards to a number bigger than starting address of AI cards, you can't access to data of that DI card.

I don't know why it happens. I'm sure there are a text or document in Siemens, but I can't found it.
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New question published by Edric is split to a separate thread with the subject User defined start address.

Best regards
Min_Moderator