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Altera_Forum's avatar
Altera_Forum
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16 years ago

Why PIO does not follow addressing rules ?

I am currently designing a custom peripheral and I have some problems with the data width. My peripheral is 8-bit data width and I would like that the access to a register takes place in the same man...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
16 years ago

What you'd really want to look at is the ".sopcinfo" file. For the PIO you will find a subsection like this: 

 <parameter name="addressAlignment">
    <type>com.altera.sopcmodel.avalon.AvalonConnectionPoint$AddressAlignment</type>
    <value>NATIVE</value>
    <derived>false</derived>
    <enabled>true</enabled>
    <visible>true</visible>
    <valid>true</valid></parameter>

It's that "NATIVE" addressing that makes the component be treated as a 32-bit wide component. Native addressing has been deprecated. See page 3-17 of the interface specification:

http://www.altera.com/literature/manual/mnl_avalon_spec.pdf

You can still use Native addressing if you'd like but it's not recommended. On the interfaces tab in the component editor, expand the little arrow that says "deprecated parameters" for your avalon slave interface. There you can select "Native Addressing".

Jake