Multiply the input by a constant

Description

The FixPt Gain block is a masked S-function that multiplies the input by a constant value (referred to as the gain). To multiply the input by a constant matrix, use the FixPt Matrix Gain block.

You specify the gain with the Gain value parameter. The gain can be a scalar or a vector. You specify the scaling for the gain with the Parameter scalingparameter. Note that there are two dialog box parameters that control the gain scaling: one associated with an edit field, and one associated with a parameter list. If Parameter data type is a generalized fixed-point number such as sfix(16), the Parameter scaling list provides you with these scaling modes:

• Use Specified Scaling - This mode uses the slope/bias or radix point-only scaling specified for the editable Parameter scaling parameter (for example, 2^-10).

• Best Precision: Element-wise - This mode produces radix points such that the precision is maximized for each element of the Gain value vector.

• Best Precision: Vector-wise - This mode produces a common radix point for each element of the Gain value vector based on the best precision for the largest value of the vector.

For a detailed description of all other block parameters, refer to Block Parameters.

Parameters and Dialog Box

Open

• Gain value - Specify as a vector or scalar.

• Parameter data type - Any data type supported by the Fixed-Point Blockset.

• Parameter scaling - Radix point-only or slope/bias scaling. Additionally, if Gain value is specified as a vector, it can be scaled using the constant vector scaling modes for maximizing precision. These scaling modes are available only for generalized fixed-point data types.

• Output data type and scaling - Specify the output data type and scaling via the dialog box, or inherit the data type and scaling from the driving block or by back propagation.

• Output data type - Any data type supported by the Fixed-Point Blockset.

• Output scaling - Radix point-only or slope/bias scaling. These scaling modes are available only for generalized fixed-point data types.

• Lock output scaling so autoscaling tool can't change it - If checked, Output scaling is locked. This feature is available only for generalized fixed-point output.

• Round toward - Rounding mode for the fixed-point output.

• Saturate to max or min when overflows occur - If checked, fixed-point overflows saturate. Otherwise, they wrap.

• Override data type(s) with doubles - If checked, the Parameter data type and Output data type values are overridden with doubles.

• Log minimums and maximums - If checked, minimum and maximum simulation values are logged to the workspace.

Conversions and Operations

The Gain value parameter is converted from doubles to the specified data type offline using round-to-nearest and saturation. Refer to Parameter Conversions for more information about parameter conversions.

The FixPt Gain block first multiples its inputs by the Gain value parameter, and then converts those results to the output data type using the specified rounding and overflow modes. Refer to Rules for Arithmetic Operations for more information about the rules this block adheres to when performing operations.

Characteristics