VHDL Programming

442 Appendix B: VHDL Reference Tables

Table B-4 Attribute Explanation Example

S’DELAYED(T) Creates a new signal delayed by T clock’DELAYED(10 ns)

S’QUIET(T) Creates a new signal that is true reset’QUIET(5 ns)

when signal Shas had no

transactions for time T; otherwise,

false

S’STABLE(T) Creates a new signal that is true clock’STABLE(1 ns)

when signal Shas had no events

for time T; otherwise, false

S’TRANSACTION Creates a signal of type BITthat load’TRANSACTION

toggles for every transaction on

signal S

S’EVENT Returns true when an event has clock’EVENT

occurred for signal Sthis delta

S’ACTIVE Returns true when a transaction load’ACTIVE

has occurred for signal Sthis delta

S’LAST_EVENT Returns the elapsed time since the data’LAST_EVENT

last event on signal S

S’LAST_ACTIVE Returns the elapsed time since the clock’LAST_ACTIVE

last transaction on signal S

S’LAST_VALUE Returns the previously assigned data’LAST_VALUE

value of signal S

Table B-5

Precedence Operator Class Operator

Highest Miscellaneous **,ABS,NOT

Multiplying *,/,MOD,REM

Sign +,-

Adding +,-,&

Relational =,/=,<,<=,>,>=

Lowest Logical AND,OR,NAND,NOR,XOR