Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
13 years ago

Making Qsys Components and Fixing Memory Problem

Dear Sir,

I practiced the tutorial named Making Qsys Components, and have a question.

(linked it following line)

ftp://ftp.altera.com/up/pub/altera_material/12.0/tutorials/making_qsys_components.pdf

like 31pages and figure 33, 34 of it, i fixed the memory from 0x00000000 to 0x00000001.

It was fixed, but the memory of 0x00000002 to 0x00000003 also changed same values.

(for example: i fixed 0x0000~0x0001 : FFFF, and also changed 0x0002~0x0003 : FFFF)

why does it changed same values?

(I think it does something to do with Avalon Interface, especially master interface.)

Thank you.

3 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    13 years ago

    That's because Avalon Interface is 32bit wide and has 4 byte enables. Read at page 6 for details.

    I guess the tutorial uses a very basic interface, so you get those aliases.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    13 years ago

    You can't change it, but you don't need to.

    You only need to implement 16bit access in the complete way. As I wrote above, the sample component in the tutorial only implements a minimal interface, without taking into account all 4 byte enable lines.

    So, if you want 2 16bit registers at memory addresses 0 and 2 (please note we are still using byte addressing) you access the first one when addr=0

    and only byteenable lines 0 and 1 are asserted; the second one shall be accessed when addr=0 with byteenable 2 and 3 asserted.