Basic Characteristics RAPID

signalxx Digital and analog signals
Description
Limitations
Predefined data
Characteristics
Data types within signalxx are used for digital and analog input and output signals.
The names of the signals are defined in the system parameters and are consequently
not to be defined in the program.
Data type Used for
signalai analog input signals
signalao analog output signals
signaldi digital input signals
signaldo digital output signals
signalgi groups of digital input signals
signalgo groups of digital output signals
Variables of the type signalxo only contain a reference to the signal. The value is set
using an instruction, e.g. DOutput.
Variables of the type signalxi contain a reference to a signal as well as a method to
retrieve the value. The value of the input signal is returned when a function is called,
e.g. DInput, or when the variable is used in a value context, e.g. IF signal_y=1 THEN.
Data of the data type signalxx may not be defined in the program. However, if this is
in fact done, an error message will be displayed as soon as an instruction or function
that refers to this signal is executed. The data type can, on the other hand, be used as a
parameter when declaring a routine.
The signals defined in the system parameters can always be accessed from the program
by using the predefined signal variables (installed data). It should however be noted
that if other data with the same name is defined, these signals cannot be used.
Signalxo is a non-value data type. Thus, data of this type does not permit valueoriented
operations.
Signalxi is a semi-value data type.
RAPID Reference Manual 7-signalxx-1