Add or subtract inputs.

Description

The FixPt Sum block is a masked S-function that performs addition or subtraction on its inputs. You specify the operations with the Enter +- characters or the number of inputs parameter. Plus-minus characters indicate the operations to be performed on the inputs:

• If there are two or more inputs, then the number of plus-minus characters must equal the number of inputs. For example, '-' requires three inputs and configures the block to subtract the second (middle) input from the first (top) input, and then add the third (bottom) input.

• If only addition of inputs is required, then a numeric parameter value equal to the number of inputs can be supplied instead of plus-minus characters.

• If only one vector is input, then a single '+' or '-' will collapse the vector using the specified operation.

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

Parameters and Dialog Box

Open

• Enter +- characters or the number of inputs - Enter as many plus or minus characters as there are inputs. For addition only, you can enter the number of inputs since this is the default operation.

• 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 Output data type is overridden with doubles.

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

Operations

The FixPt Sum block first converts the input data type(s) to the output data type using the specified rounding and overflow modes, and then performs the specified operations. Refer to Rules for Arithmetic Operations for more information about the rules this block adheres to when performing operations.

Characteristics