TABLE OF CONTENTS As we saw in previous chapters, we can use attributes to find information about types, natures and signals in a VHDL-AMS model. There are a number of predefined attributes for terminals and quantities, and we now consider them and their use.
There are two predefined attributes for terminals. Given a terminal T, these attributes are
| T'reference | An across branch quantity from T to the reference terminal of the nature of T. |
| T'contribution | A through quantity measuring the amount "flowing through" the terminal T. |
The 'reference attribute serves as a convenient way to refer to the effort applied at a terminal. It saves us having to declare a branch quantity for the terminal. For example, given an electrical terminal declared as
<b class="bold">terminal</b> bias_node : electrical;
we can specify that the voltage remain constant with the simultaneous statement
bias_node'reference == 0.5;
The 'contribution attribute refers to the flow out of the terminal into through-branch quantities declared with T as an end and into any terminal ports with which T is associated. If the terminal T is a terminal port that is associated with some terminal T1 in a port map, the quantity T'contribution is the contribution by T to the total flow out of T1. On the other hand, if T is a terminal or a terminal port that is unassociated, the energy conservation laws require that T'contribution be zero. We will return to contribution quantities in more detail in Chapter 7...
