Use of alternate register

[Taichi Ishitani]

Hi,

I'm developing CSR generation tool named RgGen and planing to IP-XACT generation.
https://github.com/rggen/rggen

I'm wondering how to interpret RgGen's CSR description into IP-XACT.
RgGen supports the indirect register type of which accessibility is controlled by other bit fields.
Eexample: 

  register {
    name 'register_11'
    offset_address 0x50
    size [2, 4]
    type [:indirect, 'register_0.bit_field_0', 'register_0.bit_field_1', ['register_0.bit_field_2', 0]]
    # bit assignments: [ 7:0] [23:16] [39:32] [55:48]
    bit_field { name 'bit_field_0'; bit_assignment lsb: 0, width: 8, sequence_size: 4, step: 16; type :rw; initial_value 0 }
    # bit assignments: [15:8] [31:24] [47:40] [63:56]
    bit_field { name 'bit_field_1'; bit_assignment lsb: 8, width: 8, sequence_size: 4, step: 16; type :rw; initial_value 0 }
  }

The register_11 register is an array register and its array size is 2 x 4.
A sub-element of this register is selected by bit fields 'register_0.bit_field_0' and 'register_0.bit_field_1'.
In addition, the 'register_11' can be accessed only when the bit field 'regiter_0.bit_field_2' is 0.

For this case, do I need to use the 'mode' element and 'alternateRegister' element to interpret this kind of regiter?

Regards,
Taichi Ishitani

[kock]

Hi Taichi,

Yes, in the latest IP-XACT version 1685-2022, you can use the mode element with sub-element condition and then you can reference that mode in an alternateRegister element.

Indirect registers with indirect addressing are described with an indirectInterface.

Best regards,
Erwin

[Taichi Ishitani]

Hi Erwin-san,

Thank you for your feedback!

From this description, I think only one bit field can be specified as the index field.
So I'm wondering whthier or not an indirect interface can be used for an indirect register which has multiple index fields.

For the above example, the 'regiter_11' register uses 'register_0.bit_field_0' and 'register_0.bit_field_1' bit fields as its index fields.

Regards,
Taichi Ishitani

[kock]

Hello Taichi,

Indeed, within one indirectInterface element one bit field can be specified. It is possible to describe multiple indirectInterface elements.

Best regards,
Erwin

[Taichi Ishitani]

Erwin, thank you for your comment.
I understand that the indirectinterface element is not suitable for the above exmaple.
I will consider another interpretation.