Simulink Reference

Signal Specification

Verify that an input signal has the specified dimensions, sample time, data type, and numeric type

Library

Signal Attributes

Description

The Signal Specification block checks that the input signal has certain specified attributes. If so, the block outputs the input signal unchanged. Otherwise, it halts the simulation and displays an error message.

The Signal Specification block can be used as a mechanism to ensure that the attributes of a signal meet the desired attributes for certain sections of your model. For example, consider two people working on different parts of a model. The Signal Specification block is useful for indicating which attributes of various signals are needed by the different sections of the model. If there is a miscommunication and data types are changed unexpectedly, the attributes do not match and Simulink reports an appropriate error. Using the Signal Specification block helps ensure that you do not introduce unexpected problems into your models. If you are familiar with the assert mechanism in languages such as C, you can see that the Signal Specification block serves a similar purpose.

The Signal Specification block can also be used to ensure correct propagation of signal attributes throughout a model. Simulink's capability of allowing many attributes to be propagated from block to block is very powerful. However, when using user-written S-functions, it is possible to create models that don't have enough information to correctly propagate attributes around the model. For these cases, the Signal Specification block is a good way of providing the information Simulink needs. Using the Signal Specification block also helps speed up model compilation when blocks are missing signal attributes.

Data Type Support

Accepts signals of any data type, including fixed-point data types but not int64 and uint64, that matches the data type specified by the Data type parameter.

Parameters and Dialog Box

Dimensions

Specify the dimensions that the input signal must match. Valid values are

• -1--Any dimension accepted
• n--Vector signal of width n accepted
• [m n]--Matrix signal having m rows and n columns accepted

Sample Time

Specify the sample time that the input signal must match. Valid values are

• -1--Any sample time accepted
• period >= 0
• [offset, period]
• [0, -1]
• [-1, -1]
  where period is the sample rate and offset is the offset of the sample period from time zero (see Sample Time).

Data type

Specify the data type that the input signal must match. To accept any data type, set this parameter to auto.

Output data type

Specify any data type, including fixed-point data types. This parameter is only visible if Specify via dialog is selected for the Data type parameter.

Output scaling value

Set the output scaling using radix point-only or [Slope Bias] scaling. This parameter is only visible if Specify via dialog is selected for the Data type parameter.

Signal type

Specify the numeric type (real or complex) that the input signal must match. To accept any numeric type, set this parameter to auto.

Sampling mode

Specify the sampling mode (sample-based or frame-based) that the input signal must match. To accept any sampling mode, set this parameter to auto.

Characteristics

Dimensionalized	Yes
Direct Feedthrough	Yes
Sample Time	Continuous
Scalar Expansion	No
Zero Crossing	No

Signal Generator

Sine Wave