Any control system has Input Signals and Output Signals. The behavior of the system can be defined in terms of how its Output Signals change in response to changes in its Input Signals. Similarly test cases verify that Output Signals respond to changes in Input Signals according to the specification. Signals are one of the fundamental building blocks in the MxSuite development environment. We have to be able to uniquely identify and classify them before we can use them for the purposes of test or specification.
A large part of managing suites of test cases is managing information about the Signals. There can be several sources for Signal information.
•The SUT has an I/O list of Signals.
•There may be one or two files that define bus messages (for example, the CAN DBC file).
•Signals that are defined and used in stating the system requirements.
•Derived Signals (such as acceleration from wheel speed).
•Internal state variables that are published during a software build process.
Below we describe the basic Signal Properties that are captured in the Signal Dictionary.
•Name - A unique string identifier for the Signal
oExceptions and exclusions
Comma, semicolon, double quote, single quote
Non-printable and white space characters (TAB, CR, LF, ..., i.e. 0 thru 0x1F and 0x7F )
oThe middle dot (·) and slash (/) are used as delimiters so should not be used in Signal names
oSquare brackets  are used for array indexes and not recommended
•Input or Output - Is it a Stimulus Signal (an input) or a Response Signal (an output)? Of course one system's outputs are another system's inputs, so unless otherwise stated the terms Stimuli and Response are always used relative to the System Under Test (SUT).
•Signal Classification - There are three basic categories:
oNumeric - An amount or level (such as RPM, temperature, On, Off, ...), or state (Park, Reverse...). Other properties of a Numeric signal are its minimum and maximum, and whether it is an integer or real.
oMessage - Data that is packed in some defined format (CAN message, Image data, C structure)
oEvent - An occurrence of some sort, such as a function call or interrupt. The word Task is used to describe Events that are function calls.
See Signal Classification for a more complete description of the classifications.
Input or Output
A Signal is an input (stimulus) to the SUT or an output (response) from it. By input we mean anything that affects how the SUT behaves. So input Signals represent not only the changing values of discrete and analog inputs and input messages, but also resets, execution of code, and the loading of files to represent EEPROM emulation.
The MxSuite enables you to manipulate one or two dimensional arrays of numeric data. See Signal Classification–Arrays.