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Verilog AXI Stream Components Readme

For more information and updates: http://alexforencich.com/wiki/en/verilog/axis/start

GitHub repository: https://github.com/alexforencich/verilog-axis

Introduction

Collection of AXI Stream bus components. Most components are fully parametrizable in interface widths. Includes full MyHDL testbench with intelligent bus cosimulation endpoints.

Documentation

arbiter module

General-purpose parametrizable arbiter. Supports priority and round-robin arbitration. Supports blocking until request release or acknowledge.

axis_adapter module

The axis_adapter module bridges AXI stream busses of differing widths. The module is parametrizable, but there are certain restrictions. First, the bus word widths must be identical (e.g. one 8-bit lane and eight 8-bit lanes, but not one 16-bit lane and one 32-bit lane). Second, the bus widths must be related by an integer multiple (e.g. 2 words and 6 words, but not 4 words and 6 words). Wait states will be inserted on the wider bus side when necessary.

axis_arb_mux_N module

Frame-aware AXI stream arbitrated muliplexer with parametrizable data width. Supports priority and round-robin arbitration.

Can be generated with arbitrary port counts with axis_arb_mux.py.

axis_async_fifo module

Basic word-based asynchronous FIFO with parametrizable data width and depth. Supports power of two depths only.

axis_async_frame_fifo module

Basic frame-based asynchronous FIFO with parametrizable data width and depth. Supports power of two depths only.

axis_crosspoint module

Basic crosspoint switch. tready signal not supported. Parametrizable data width.

Can be generated with arbitrary port counts with axis_crosspoint.py.

axis_demux_N module

Frame-aware AXI stream demuliplexer with parametrizable data width.

Can be generated with arbitrary port counts with axis_demux.py.

axis_fifo module

Basic word-based synchronous FIFO with parametrizable data width and depth. Supports power of two depths only.

axis_frame_fifo module

Basic frame-based synchronous FIFO with parametrizable data width and depth. Supports power of two depths only.

axis_frame_join_N module

Frame joiner with optional tag. 8 bit data path only.

Can be generated with arbitrary port counts with axis_frame_join.py.

axis_frame_length_adjust module

Frame length adjuster module. Truncates or pads frames as necessary to meet the specified minimum and maximum length. Reports the original and current lengths as well as whether the packet was truncated or padded. Length limits are configurable at run time.

axis_frame_length_adjust_fifo module

Frame length adjuster module with FIFO. Truncates or pads frames as necessary to meet the specified minimum and maximum length. Reports the original and current lengths as well as whether the packet was truncated or padded. FIFOs are used so that the status information can be read before the packet itself. Length limits are configurable at run time.

axis_ll_bridge module

AXI stream to LocalLink bridge.

axis_mux_N module

Frame-aware AXI stream muliplexer with parametrizable data width.

Can be generated with arbitrary port counts with axis_mux.py.

axis_rate_limit module

Fractional rate limiter, supports word and frame modes. Inserts wait states to limit data rate to specified ratio. Frame mode inserts wait states at end of frames, word mode ignores frames and inserts wait states at any point. Parametrizable data width. Rate and mode are configurable at run time.

axis_register module

Datapath register. Use to improve timing for long routes.

axis_srl_fifo module

SRL-based FIFO. Good for small FIFOs. SRLs on Xilinx FPGAs have a very fast input setup time, so this module can be used to aid in timing closure.

axis_srl_register module

SRL-based register. SRLs on Xilinx FPGAs have a very fast input setup time, so this module can be used to aid in timing closure.

axis_stat_counter module

Statistics counter module. Counts bytes and frames passing through monitored AXI stream interface. Trigger signal used to reset and dump counts out of AXI interface, along with tag value. Use with axis_frame_join_N to form a single monolithic frame from multiple monitored points with the same trigger.

axis_switch_NxN module

Frame-aware AXI stream switch with parametrizable data width.

Can be generated with arbitrary port counts with axis_switch.py.

axis_tap module

AXI stream tap module. Used to make a copy of an AXI stream bus without affecting the bus. Back-pressure on the output results in truncated frames with tuser set.

ll_axis_bridge module

LocalLink to AXI stream bridge.

priority_encoder module

Parametrizable priority encoder.

Common signals

tdata   : Data (width generally DATA_WIDTH)
tkeep   : Data word valid (width generally KEEP_WIDTH)
tvalid  : Data valid
tready  : Sink ready
tlast   : End-of-frame
tid     : Identifier tag (width generally ID_WIDTH)
tdest   : Destination tag (width generally DEST_WIDTH)
tuser   : User sideband signals (width generally USER_WIDTH)

Common parameters

DATA_WIDTH           : width of tdata signal
KEEP_ENABLE          : enable tkeep signal (default DATA_WIDTH>8)
KEEP_WIDTH           : width of tkeep signal (default DATA_WIDTH/8)
LAST_ENABLE          : enable tlast signal
ID_ENABLE            : enable tid signal
ID_WIDTH             : width of tid signal
DEST_ENABLE          : enable tdest signal
DEST_WIDTH           : width of tdest signal
USER_ENABLE          : enable tuser signal
USER_WIDTH           : width of tuser signal
USER_BAD_FRAME_VALUE : value of tuser indicating bad frame
USER_BAD_FRAME_MASK  : bitmask for tuser bad frame indication

Source Files

arbiter.v                          : General-purpose parametrizable arbiter
axis_adapter.v                     : Parametrizable bus width adapter
axis_arb_mux.py                    : Arbitrated multiplexer generator
axis_arb_mux_4.v                   : 4 port arbitrated multiplexer
axis_async_fifo.v                  : Asynchronous FIFO
axis_async_frame_fifo.v            : Asynchronous frame FIFO
axis_crosspoint.py                 : Crosspoint switch generator
axis_crosspoint_4x4.v              : 4x4 crosspoint switch
axis_demux.py                      : Demultiplexer generator
axis_demux_4.v                     : 4 port demultiplexer
axis_fifo.v                        : Synchronous FIFO
axis_frame_fifo.v                  : Synchronous frame FIFO
axis_frame_join.py                 : Frame joiner generator
axis_frame_join_4.v                : 4 port frame joiner
axis_frame_length_adjust.v         : Frame length adjuster
axis_frame_length_adjust_fifo.v    : Frame length adjuster with FIFO
axis_ll_bridge.v                   : AXI stream to LocalLink bridge
axis_mux.py                        : Multiplexer generator
axis_mux_4.v                       : 4 port multiplexer
axis_rate_limit.v                  : Fractional rate limiter
axis_register.v                    : AXI Stream register
axis_srl_fifo.v                    : SRL-based FIFO
axis_srl_register.v                : SRL-based register
axis_switch.py                     : AXI stream switch generator
axis_switch_4x4.v                  : 4x4 port AXI stream switch
axis_stat_counter.v                : Statistics counter
axis_tap.v                         : AXI stream tap
ll_axis_bridge.v                   : LocalLink to AXI stream bridge
priority_encoder.v                 : Parametrizable priority encoder

AXI Stream Interface Example

two byte transfer with sink pause after each byte

          __    __    __    __    __    __    __    __    __
clk    __/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__
                _____ _________________
tdata  XXXXXXXXX_D0__X_D1______________XXXXXXXXXXXXXXXXXXXXXXXX
                _____ _________________
tkeep  XXXXXXXXX_K0__X_K1______________XXXXXXXXXXXXXXXXXXXXXXXX
                _______________________
tvalid ________/                       \_______________________
       ______________             _____             ___________
tready               \___________/     \___________/
                      _________________
tlast  ______________/                 \_______________________

tuser  ________________________________________________________

two back-to-back packets, no pauses

          __    __    __    __    __    __    __    __    __
clk    __/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__
                _____ _____ _____ _____ _____ _____
tdata  XXXXXXXXX_A0__X_A1__X_A2__X_B0__X_B1__X_B2__XXXXXXXXXXXX
                _____ _____ _____ _____ _____ _____
tkeep  XXXXXXXXX_K0__X_K1__X_K2__X_K0__X_K1__X_K2__XXXXXXXXXXXX
                ___________________________________
tvalid ________/                                   \___________
       ________________________________________________________
tready
                            _____             _____
tlast  ____________________/     \___________/     \___________

tuser  ________________________________________________________

bad frame

          __    __    __    __    __    __
clk    __/  \__/  \__/  \__/  \__/  \__/  \__
                _____ _____ _____
tdata  XXXXXXXXX_A0__X_A1__X_A2__XXXXXXXXXXXX
                _____ _____ _____
tkeep  XXXXXXXXX_K0__X_K1__X_K2__XXXXXXXXXXXX
                _________________
tvalid ________/                 \___________
       ______________________________________
tready
                            _____
tlast  ____________________/     \___________
                            _____
tuser  ____________________/     \___________

Testing

Running the included testbenches requires MyHDL and Icarus Verilog. Make sure that myhdl.vpi is installed properly for cosimulation to work correctly. The testbenches can be run with a Python test runner like nose or py.test, or the individual test scripts can be run with python directly.

Testbench Files

tb/axis_ep.py        : MyHDL AXI Stream endpoints
tb/ll_ep.py          : MyHDL LocalLink endpoints

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