Visible to Intel only — GUID: hco1423077154915
Ixiasoft
Visible to Intel only — GUID: hco1423077154915
Ixiasoft
14.4.34. Look-Up Table (Lut)
q = LUT[a]
The size of the table determines the size of the initialization arrays.
Parameter | Description |
---|---|
Output data type mode | Determines how the block sets its output data type:
|
Output data type | Specifies the output data type. For example, sfix(16), uint(8). |
Output scaling value | Specifies the output scaling value. For example, 2^-15. |
Output value map | Specifies the location of the output values. For example, round([0;254]/17). This parameter may also be a fi object when specifying data of arbitrarily high precision. |
Floating point precision | Specifies the floating-point precision. For example, float32_m23. |
You can specify the contents of the Lut block in one of the following ways:
- Specify table contents with a single row or column vector. The length of the 1D row or column vector determines the number of addressable entries in the table. If DSP Builder reads vector data from the table, all components of a given vector share the same value.
- When a look-up table contains vector data, you can provide a matrix to specify the table contents. The number of rows in the matrix determines the number of addressable entries in the table. Each row specifies the vector contents of the corresponding table entry. The number of columns must match the vector length, otherwise DSP Builder issues an error.
Every Primitive library block accepts double-precision floating-point values when specifying mask parameters. This format limits precision to no more than 53 bits, which is more than sufficient for most of the blocks. For higher precision, the Const, DualMem, or LUT blocks optionally accept values using Simulink's Fixed Point data type. For example:
constValue = fi(0.142, 1, 16, 15)
vectorValue = fi(sin([0:10]'), 1, 18, 15)
To configure a Const, DualMem, or LUT with data of precision higher than IEEE double precision, create a MATLAB fi object of the required precision that contains the high precision data. Avoid truncation when creating this object. Use the fi object to specify the Value of the Const, the Initial Contents of the DualMem block, or the Output value map of the LUT block.
Signal | Direction | Type | Description | Vector Data Support | Complex Data Support |
---|---|---|---|---|---|
a | Input | Any fixed--point type | Operand | Yes | No |
q | Output | Derived fixed- or floating-point type | Result | Yes | Yes (with output value map) |