Sum (Simulink Reference)

Add or subtract inputs

Library

Math Operations

Description

The Sum block performs addition or subtraction on its inputs. This block can add or subtract scalar, vector, or matrix inputs. It can also collapse the elements of a single input vector.

You specify the operations of the block with the List of Signs parameter. Plus (+), minus (-), and spacer (|) characters indicate the operations to be performed on the inputs:

If there are two or more inputs, then the number of 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.

All nonscalar inputs must have the same dimensions. Scalar inputs will be expanded to have the same dimensions as the other inputs.

A spacer character creates extra space between ports on the block's icon.
If only addition of all inputs is required, then a numeric parameter value equal to the number of inputs can be supplied instead of "+" characters.
If only one vector is input, then a single "+" or "-" will collapse the vector using the specified operation.

The 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.

Data Type Support

The Sum block accepts real or complex signals of any data type supported by Simulink, including fixed-point data types. The inputs may be of different data types unless you select the Require all inputs to have same data type parameter.

For a discussion on the data types supported by Simulink, refer to Data Types Supported by Simulink in the Using Simulink documentation.

Parameters and Dialog Box

The Main pane of the Sum block dialog appears as follows:

Icon shape: Designate the icon shape of the block.
List of signs: Enter as many plus (+) and minus (-) characters as there are inputs. Addition is the default operation, so if you only want to add the inputs, enter the number of input ports. For a single vector input, "+" or "-" will collapse the vector using the specified operation.; You can manipulate the positions of the input ports on the block by inserting spacers (|) between the signs in the List of signs parameter. For example, "++|--" creates an extra space between the second and third input ports.
Sample time (-1 for inherited): Specify the time interval between samples. To inherit the sample time, set this parameter to -1. See Specifying Sample Time in the online documentation for more information.

The Signal data types pane of the Sum block dialog appears as follows:

Require all inputs to have same data type: Select this parameter to require that all inputs must have the same data type.
Output data type mode: Specify the output data type and scaling to be the same as the first input, or inherit the data type and scaling from an internal rule or by backpropagation. You can also choose a built-in data type from the drop-down list. Lastly, if you choose Specify via dialog, the Output data type, Output scaling value, and Lock output scaling against changes by the autoscaling tool parameters become visible.
Output data type: Specify any data type, including fixed-point data types. This parameter is only visible if you select Specify via dialog for the Output data type mode parameter.
Output scaling value: Set the output scaling using binary point-only or [Slope Bias] scaling. This parameter is only visible if you select Specify via dialog for the Output data type mode parameter.
Lock output scaling against changes by the autoscaling tool: Select to lock scaling of outputs. This parameter is only visible if you select Specify via dialog for the Output data type mode parameter.
Round integer calculations toward: Select the rounding mode for fixed-point operations.
Saturate on integer overflow: Select to have overflows saturate.

Characteristics

Direct Feedthrough
Yes

Sample Time
Specified in the Sample time parameter

Scalar Expansion
Yes

States
0

Dimensionalized
Yes

Zero Crossing
No

Direct Feedthrough	Yes
Sample Time	Specified in the Sample time parameter
Scalar Expansion	Yes
States	0
Dimensionalized	Yes
Zero Crossing	No

Subtract Sum of Elements