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PeakRDL-regblock/docs/cpuif/apb3.rst
2022-02-21 22:16:56 -08:00

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AMBA 3 APB
==========
Implements the register block using an
`AMBA 3 APB <https://developer.arm.com/documentation/ihi0024/b/Introduction/About-the-AMBA-3-APB>`_
CPU interface.
The APB3 CPU interface comes in two i/o port flavors:
SystemVerilog Interface
Class: :class:`peakrdl.regblock.cpuif.apb3.APB3_Cpuif`
Interface Definition: :download:`apb3_intf.sv <../../test/lib/cpuifs/apb3/apb3_intf.sv>`
Flattened inputs/outputs
Flattens the interface into descrete input and output ports.
Class: :class:`peakrdl.regblock.cpuif.apb3.APB3_Cpuif_flattened`
.. warning::
Some IP vendors will incorrectly implement the address signalling
assuming word-addresses. (that each increment of ``PADDR`` is the next word)
For this exporter, values on the interface's ``PADDR`` input are interpreted
as byte-addresses. (a 32-bit APB bus increments ``PADDR`` in steps of 4)
Although APB protocol does not allow for unaligned transfers, this is in
accordance to the official AMBA bus specification.
Be sure to double-check the interpretation of your interconnect IP. A simple
bit-shift operation can be used to correct this if necessary.