axi4lite.rst

AXI4-Lite protocol

The AXI4-Lite protocol is part of AMBA4 protocols defined by ARM. The specification is open and broadly adopted.

This document is not intended as a full ddescription of the protocol, instead it focuses on the implementation used in Red Pitaya RTL modules.

Protocol design

The interface is split into 5 data streams:

• write address
• write data
• write response
• read address
• read data and response

Each stream has its own handshaking signals, so they can handled separately. For example to solve timing issues each of the streams can register forward signals or the backpressure signal separately from the other streams. This separation also allows for interconnect components (arbiters, address decoders) to be optimized depending on trafic patterns on each of the streams.

signal	description
ACLK
ARESETn
AWADDR
AWPROT
AWVALID
AWRERADY

.. wavedrom::

   {signal: [
     ['system',
       {name: 'ACLK'   , wave: 'p.....|...'},
       {name: 'ARESETn', wave: 'x.345x|=.x', data: ['head', 'body', 'tail', 'data']},
     ],
     {},
     ['write address',
       {name: 'AWADDR' , wave: '0.1..0|1.0'},
       {name: 'AWPROT' , wave: '0.1..0|1.0'},
       {name: 'AWVALID', wave: '1.....|01.'},
       {name: 'AWREADY', wave: '1.....|01.'},
     ],
     {},
     ['write data',
       {name: 'WDATA'  , wave: '1.....|01.'},
       {name: 'WSTRB'  , wave: '1.....|01.'},
       {name: 'WVALID' , wave: '1.....|01.'},
       {name: 'WREADY' , wave: '1.....|01.'},
     ],
     {},
     ['write response',
       {name: 'BRESP'  , wave: '1.....|01.'},
       {name: 'BVALID' , wave: '1.....|01.'},
       {name: 'BREADY' , wave: '1.....|01.'},
     ],
     {},
     ['read address',
       {name: 'ARADDR' , wave: '0.1..0|1.0'},
       {name: 'ARPROT' , wave: '0.1..0|1.0'},
       {name: 'ARVALID', wave: '1.....|01.'},
       {name: 'ARREADY', wave: '1.....|01.'},
     ],
     {},
     ['read data',
       {name: 'RDATA'  , wave: '1.....|01.'},
       {name: 'RRESP'  , wave: '1.....|01.'},
       {name: 'RVALID' , wave: '1.....|01.'},
       {name: 'RREADY' , wave: '1.....|01.'}
     ]
   ]}