Resource sharing is an area optimization in which HDL Coder™ identifies multiple functionally equivalent resources and replaces them with a single resource. The data is time-multiplexed over the shared resource to perform the same operations. To learn more about how resource sharing works, see Resource Sharing.
You can follow these guidelines to learn how to use the resource sharing optimization effectively for subsystems such as atomic subsystems and MATLAB Function blocks, and with floating-point IPs. Each guideline has a severity level that indicates the level of compliance requirements. To learn more, see HDL Modeling Guidelines Severity Levels.
3.1.5
Recommended
To share resources for identical subsystems, such as when grouping Product, Add, and Delay blocks to map to one DSP slice, the subsystems to be shared must be Atomic Subsystem blocks or MATLAB Function blocks.
Determine whether you want to share resources at the existing clock rate or at a higher clock rate.
Sharing of enabled subsystems is not supported. For sharing resources, use atomic subsystems without enable semantics.
Specify a SharingFactor that is greater than or equal to the number of subsystems that you want to share.
For example, if you have 10 atomic subsystems,
and you set the SharingFactor to
5, HDL Coder cannot implement the resource sharing to
2 instances of the subsystem. To share the
subsystems, divide the subsystems, and then share the instances of
the smaller subsystems.
Check the SharingFactor that you specify for various subsystems. The resource sharing optimization overclocks the shared resources by the LCM (Least Common Multiple) of the SharingFactor of various subsystems.
For example, if you specify a SharingFactor
of 5 for one Subsystem, and a
SharingFactor of 7 for
another Subsystem, the resource sharing optimization
overclocks the shared resources by 35. In such
cases, it is recommended that you use the same
SharingFactor for both subsystems, such as
5 or 7. To learn more
about this calculation, see How Resource Sharing Works.
3.1.6
Recommended
HDL Coder shares MATLAB Function blocks that have:
The same Simulink® checksum. Use Simulink.Subsystem.getChecksum
to determine the checksum.
The same HDL block properties.
Make sure that the blocks do not use:
Persistent variables
Loop streaming
Output pipelining
By using the MATLAB Datapath architecture, you can share
resources inside the MATLAB Function block and across the
MATLAB Function block with other blocks in your Simulink model. When you use this architecture, the code generator treats
the MATLAB Function block like a regular Subsystem
block. This capability enables you to more widely apply various speed and area
optimizations with MATLAB Function blocks. See HDL Optimizations Across MATLAB Function Block Boundary Using MATLAB Datapath Architecture.
3.1.7
Recommended
HDL Coder can share Atomic Subsystem blocks that have the same Simulink checksum and the same HDL block properties.
To share Atomic Subsystem blocks, the state elements that the blocks can contain are:
Delay
Unit Delay
Unit Delay Enabled Synchronous
Unit Delay Resettable Synchronous
Unit Delay Enabled Resettable Synchronous
The state elements must have the Initial condition parameter set to 0.
Sharing of atomic subsystems inside enabled subsystems with synchronous semantics is not supported. To share resources, use enabled subsystems with classic semantics.
You cannot share atomic subsystems that contain the following blocks or block implementations:
Detect Change
Discrete Transfer Fcn
HDL FFT
HDL FIFO
Math Function (conj, hermitian, transpose)
MATLAB Function blocks that contain persistent variables
Sqrt
Cascade architecture (MinMax, Product, Sum)
CORDIC architecture
Reciprocal Newton architecture
Filter blocks including Discrete FIR Filter
Communications Toolbox™ blocks
DSP System Toolbox™ blocks, except Discrete FIR Filter
Stateflow® blocks
Blocks that are not supported for delay balancing. For details, see Delay Balancing Limitations.
HDL Coder can share Atomic Subsystem blocks that have the same Simulink checksum and the same HDL block properties.
If you want to share Atomic Subsystem blocks, the state elements that the blocks can contain are:
Delay
Unit Delay
Unit Delay Enabled Synchronous
Unit Delay Resettable Synchronous
Unit Delay Enabled Resettable Synchronous
The state elements must have the Initial condition parameter set to 0.
You cannot share atomic subsystems that contain the following blocks or block implementations:
Detect Change
Discrete Transfer Fcn
HDL FFT
HDL FIFO
Math Function (conj, hermitian, transpose)
MATLAB Function blocks that contain persistent variables
Sqrt
Cascade architecture (MinMax, Product, Sum)
CORDIC architecture
Reciprocal Newton architecture
Filter blocks including Discrete FIR Filter
Communications Toolbox blocks
DSP System Toolbox blocks, except Discrete FIR Filter
Stateflow blocks
Blocks that are not supported for delay balancing. For details, see Delay Balancing Limitations.
3.1.8
Recommended
To share multiple:
Floating-point adders, set ShareAdders to
on.
Floating-point multipliers, make sure
ShareMultipliers is set to on.
Other floating-point resources, set
ShareFloatingPointIP to on.
See also Modeling with Native Floating Point.