AXI4-Stream to Software
Libraries:
SoC Blockset /
Memory
Description
The AXI4-Stream to Software block models a connection between hardware logic and a software task through external memory. The writer puts data into the channel using a MathWorks® simplified AXI stream protocol and the reader (processor) gets data from a DMA driver interface. The block models the datapath and software stack of that connection, including a FIFO, DMA engine, interconnect and external memory, interrupts, kernel buffer management of the DMA driver, and data transfers to the software task.
This block is equivalent to a Memory Channel block with the
Channel type parameter set to AXI4-Stream to Software via
DMA
connected to a Memory Controller block.
Since the memory controller is implicit to the design - you can instantiate several memory blocks that connect to the same memory unit via a memory controller. Valid blocks are:
The maximum number of manager interfaces in a model is 16.
For more information about the MathWorks simplified AXI stream protocol, see AXI4-Stream Interface.
Examples
Streaming Data from Hardware to Software
A systematic approach to design the data-path between hardware logic (FPGA) and embedded processor using SoC Blockset™.
Ports
Input
wrData — Writer data bus signal
scalar | vector | matrix
This signal contains the data to the memory.
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
| Boolean
| fixed point
wrCtrlIn — Writer input control signal
bus
This port represents the protocol from the data producer to the processor. The
AXI4-Stream to Software block checks this signal when using
wrData. The signals on the control bus are of type
StreamM2SBusObj
. To create this control bus, use the SoC Bus Creator block. For more information about bus types, see External Memory Channel Protocols.
Data Types: StreamM2SBusObj
done — Notification message of completed read
scalar
This message port receives a notification from the connected Stream Read block. The notification indicates that a read transaction completed. For more information on messages, see Messages.
Data Types: Boolean
Output
event — Task read event signal
scalar
This port sends a task event signal that triggers the Task Manager block to execute the associated event-driven read.
Data Types: rteEvent
msg — Output data signal to software
scalar | vector | matrix
This signal contains the data read from the memory, sent as a message to the connected Stream Read block. For more information on messages, see Messages.
Data Types: SoCData
wrCtrlOut — Writer control signal to data producer
bus
This bus represents the protocol bus from the memory channel to the data producer.
The signals on the bus are of type StreamS2MBusObj
. To separate the
signal from the bus, use the SoC Bus Selector block.
Data Types: StreamS2MBusObj
Parameters
Memory simulation — Set simulation timing accuracy
Burst accurate
(default) | Protocol accurate
| Behavioral
Memory simulation provides three levels of timing resolution. Select one of these options:
Burst accurate — Simulates memory contention and high-resolution timing.
Protocol accurate — Simulates AXI4 protocol hand-shaking sequencing and low-resolution timing.
Behavioral — Simulates data transactions only and no timing.
When this parameter is set to Behavioral mode, the value of the
TLAST
signal is ignored.
Main
Memory selection — Choose between memory regions
PS memory
(default) | PL memory
Select between processing subsystem (PS) or programming logic (PL) memory.
If the selected board supports only PL memory, then the default value is
PL memory
.If the selected board supports only PS memory or only PL memory, then this parameter is read-only.
If the selected board is not a supported SoC board, then this parameter is not visible.
Region size (bytes) — Size of the allocated memory region, in bytes
calculated
This parameter is read-only.
The of the region size in bytes. This value is calculated as the number of buffers multiplied by the size of the buffer. The size of the buffer is defined as the size of the data multiplied by the software frame size. Define this value by setting the Data type and Dimensions parameters on the Signal Attributes tab.
Example: A software frame size of 1024 uint32 defines a buffer of 4096 Bytes. If the number of buffers is set to 2, the region size is 8192 bytes.
Number of buffers — Number of buffers in region
8
(default) | integer
Define the number of buffers in the memory.
The memory access has a ring-buffer pattern. The writer can continually write as long as buffers are available. When a buffer is completed, it becomes available for the reader. The writer and reader traverse the buffers in a circular pattern. As long as the writer and reader maintain similar rates, the buffering prevents blockage.
A disparate rate between a reader and a writer slows down the faster device. For example, a slow reader causes the writer to run out of buffers and blocks the writer, effectively slowing down the writer to the reader rate. Likewise, a slow writer causes the reader to run out of buffers and blocks the reader, effectively slowing down the reader to the writer rate.
The Number of buffers parameter must be an integer from 3 to 64.
Burst length — Burst length for memory transactions
256
(default) | scalar
The length of bursts for this connection on the memory bus in units of scalar data. The scalar unit is the packed data type. Specify the burst size for both writer and reader access to the channel.
The channel data is always transferred to the memory model using burst transactions. For the AXI4 configuration, the algorithm logic is responsible for defining the burst through the protocol signals.
The Burst length parameter determines the burst size to the memory, and the wrData signal defines the size of each transfer on the interface.
FIFO depth (number of bursts) — Depth of FIFO for data
8
(default) | scalar
Specify the depth of the data FIFO, in units of bursts. When the writer has no buffers to write to, the FIFO can absorb data until a buffer becomes available. This value is the maximum number of bursts that the FIFO can buffer before it drops data.
Dependencies
To enable this parameter, select Burst accurate under Memory simulation.
FIFO almost-full depth (number of bursts) — Depth of FIFO when backpressure is asserted
6
(default) | scalar
Specify a number that asserts a backpressure signal from the channel to the data source. To avoid dropping data, set a high watermark, allowing the data producer enough time to react to backpressure. This number must be smaller than the FIFO depth.
Dependencies
To enable this parameter, select Burst accurate under Memory simulation.
Clock frequency (MHz) — Interconnect frequency of manager datapath
100
(default)
Specify the frequency of the manager datapath in MHz.
Dependencies
To enable this parameter, select Burst accurate under Memory simulation.
Data width (bits) — Data width of manager datapath
64
(default) | scalar
Specify the data width of the manager datapath to the interconnect controller in bits.
Dependencies
To enable this parameter, select Burst accurate under Memory simulation.
Signal Attributes
Stream data signalDimensions — Dimensions of input data signal
1 (default) | scalar | array
wrData can be a multidimensional array. Specify the dimension for the array as a whole number.
Example: 1 — A scalar sample.
Example: [10 1] — A vector of ten scalars.
Example: [1080 1920 3] — A 1080p frame. The frame includes 1080 lines of 1920 pixels per line, and each pixel is represented by three values (for red, green, and blue).
Data type — Data type of writer data
uint32
(default) | double
| single
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint64
| Boolean
| fixed point
Specify the data type of the wrData port. For help, click the ... button and select Data Type Assistant.
Sample time — Time interval of sampling
1 (default) | positive scalar | vector
Specify a time interval in seconds to define how often the block updates.
When you do not want the output to have a time offset, specify the
Sample time parameter as a scalar. To add a time offset to
the output, specify the Sample time parameter as a
1
-by-2
vector, where the first element is the
sampling period and the second element is the offset. For more information about
sample times in Simulink®, see Specify Sample Time.
Enable sample packing (last signal dimension as channel) — Pack data on the last dimension of the signal
off
(default) | on
Select this parameter to enable data packing across the last dimension of the
signal. The AXI4-Stream to Software block packs the data along the last
dimension of the signal. For example, if the channel data type is
uint32
, the dimensions are [1024 4]
. If you
select this sample packing parameter, then the memory channel generates 1024 read or
write transactions of 128 bits. If you clear this sample packing parameter, the memory
channel generates 4096 transactions of 32 bits each.
This figure shows how data is aligned for a signal with data type
fixdt10[4x3]
. When the data is packed, three 10-bit words are
concatenated and extended by 2 bits to a 32-bit word. When the data is not packed,
each 10-bit word is extended to a 16-bit word.
This figure shows how data is aligned for a signal with data type
uint8[8x3]
. When the data is packed, three 8-bit words are
concatenated and extended by 8 bits to a 32-bit word. When the data is not packed,
each 8-bit word is represented as an 8-bit sample.
The combined width of the flattened signal must not exceed 512 bits.
Dimensions — Dimensions of software data
scalar
Specify the dimension for the software data (reader) as a whole number.
The default value is 1024
.
Data type — Data type of software data
Inherit: Same as input
(default) | uint16
| uint32
| uint64
| fixdt(0,128,0)
Specify the data type of the software data (reader). For help, click the ... button and select Data Type Assistant. By default, this value is set to inherit the data type from the source signal.
Performance
Local masterView performance plots — Display performance metrics
button
Clicking the button opens performance plots for the local master in a new window. For more information about performance graphs, see Memory Channel Latency Plots.
Dependencies
To enable this parameter, select Burst accurate under Memory simulation.
View performance plots — Display performance metrics
button
Clicking the button opens the Performance Plots for Memory Controller window. You can then select to plot bandwidth, bursts, or latencies. For more information about performance graphs, see Memory Controller Latency Plots.
Dependencies
To enable this parameter, select Burst accurate under Memory simulation.
Extended Capabilities
HDL Code Generation
Generate VHDL, Verilog and SystemVerilog code for FPGA and ASIC designs using HDL Coder™.
Fixed-Point Conversion
Design and simulate fixed-point systems using Fixed-Point Designer™.
Version History
Introduced in R2022bR2023b: Support for multiple AXI streams
Use multiple AXI4-Stream to Software, Software to AXI4-Stream, or Memory Channel blocks to model, simulate, and deploy designs with multiple streams to and from software. In previous releases, SoC Blockset™ supported multiple streams for modeling only. This release adds the ability to generate binaries and software and deploy it on SoC devices.
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