Log2 HDL Optimized

R2026b

Compute base-2 logarithm of input

Since R2026b

• 

Log2 HDL Optimized block

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Libraries:
Fixed-Point Designer HDL Support / Math Operations

Description

The Log2 HDL Optimized block computes the base-2 logarithm of an input. This block is optimized for efficient HDL code generation with HDL Coder™.

Ports

Input

u — Value to compute base-2 logarithm of

real-valued scalar | vector | matrix

Value to compute base-2 logarithm of, specified as a real-valued scalar, vector, or matrix. Fixed-point inputs must use binary-point scaling.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | fixed point

validIn — Whether input is valid

scalar

Whether input is valid, specified as a Boolean scalar. This control signal indicates when the data from the u input port is valid. When this value is 1 (true), the block captures the value at the u input port. When this value is 0 (false), the block ignores the input samples.

Data Types: Boolean

Output

log₂u — Base-2 logarithm of input

scalar | vector | matrix

Base-2 logarithm of input, returned as a scalar, vector, or matrix the same size as the input u. For fixed-point inputs, the block returns a signed fixed-point data type. For floating-point inputs, the output data type is the same as the input data type.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | fixed point

validOut — Whether output data is valid

scalar

Whether output data is valid, returned as a Boolean scalar. When the value of this control signal is 1 (true), the block has successfully computed the output. When this value is 0 (false), the output data is not valid.

Data Types: Boolean

logZero — Whether value at output port is result of log2(0)

scalar | vector | matrix

Whether value at output port is the result of log2(0), returned as a Boolean scalar, vector, or matrix. When the value of this port is 1 (true), the block has processed an input value of 0. When the value of this port is 0 (false), the block has processed a nonzero input value.

Tips

When the value at the logZero port is 1 (true), the output saturates to the maximum that the output data type allows.

Dependencies

To enable this port, select the Show Zero In Port parameter.

Data Types: Boolean

Parameters

To edit block parameters interactively, use the Property Inspector. From the Simulink^® Toolstrip, on the Simulation tab, in the Prepare gallery, select Property Inspector.

Show Zero In Port — Whether block shows logZero port

on (default) | off

Whether the block shows the logZero port.

Programmatic Use

To set the block parameter value programmatically, use the set_param function.

To get the block parameter value programmatically, use the get_param function.

Parameter:	ShowZeroIn
Values:	1or true (default) | 0 or false
Data Types:	logical

Example: set_param(gcb,ShowZeroIn = 0)

Algorithms

Latency

The latency of the Log2 HDL Optimized block depends on the data type of the input. The latency is:

• 8 for unsigned integer and fixed-point data types

• 10 for signed integer, signed fixed-point, and floating-point data types

Extended Capabilities

HDL Code Generation
Generate VHDL, Verilog and SystemVerilog code for FPGA and ASIC designs using HDL Coder™.

Version History

Introduced in R2026b