4.3.5 Comparison of resource types

In general, it is clear from the context whether a piece of state that an instance exposes is an initialization-time parameter, a run-time parameter, or a register. If it is unclear, see the following table.

In this table, if criterion is true, the value can be modeled as shown, reading from left to right:

Table 4-2 Comparison of resource types

Criterion

Generic resource Initialization-time parameter Run-time parameter Register
Value is configurable at initialization time. no yes yes no
Value is modifiable at runtime. yes no yes yes
Value is modifiable at runtime and generally does not change at runtime except when the user changes it. yes no yes usually no
Value can change spontaneously, that is, without a parameter write, during runtime. yes no no yes
Is an architectural register. no no no yes
Register that has a reset value. no no no yes
Register that is not reset during simulation reset. no yes yes no
Corresponds to a design-time parameter of the hardware. no yes no no
Corresponds to a hardware register. no no no yes
Can be modified by program code. usually no no no yes
Is artificial, not present in the hardware. yes yes yes usually no
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