VHDL Programming

62 Chapter Three WAIT ON Signal We have already seen an example of the first type in the previous process example. The WAIT ONsi ...

Sequential Processing 63 statement following the WAIT statement. A couple of examples are shown here: WAIT FOR 10 ns; WAIT FOR ( ...

64 Chapter Three WAIT Time-Out There are instances while designing a model when you are not sure that a condition will be met. T ...

Sequential Processing 65 WAIT UNTIL sendA = 1; Execution stops at the first WAITstatement of the process even though the express ...

66 Chapter Three REPORT “sendA timed out at ‘ 1 ’” SEVERITY ERROR; sendB <= ‘ 1 ’ AFTER 10 ns; end PROCESS B; END wait_timeou ...

Sequential Processing 67 Concurrent Assignment Problem One of the problems that most designers using sequential signal assignmen ...

68 Chapter Three This statement inside of a process statement schedules an event for signal selon the next delta time point, wit ...

Sequential Processing 69 have a sensitivity list. A sensitivity list implies that execution starts from the beginning of the pro ...

70 Chapter Three Passive Processes Passive processes are processes that exist in the entity statement part of an entity. They ar ...

Sequential Processing 71 . . . END struct; ARCHITECTURE switch OF dff IS BEGIN . . . . END switch; This example shows the entity ...

72 Chapter Three that is sensitive to the signal in its expression. For instance, the first as- sertion is sensitive to signal A ...

Chapter 4 Data Types In this chapter, we examine the object types used in VHDL. The types allowed in VHDL consist of everything ...

74 Chapter Four Object Types A VHDL object consists of one of the following: Signal, which represents interconnection wires tha ...

Data Types 75 USE IEEE.std_logic_1164.ALL; ENTITY board_design is PORT( data_in : IN bus_type; PORT( data_out : OUT bus_type); S ...

76 Chapter Four for board_design. The signal sys_clkcan therefore be assigned to and read from in entity board_designand archite ...

Data Types 77 delay := 4.5 ns; ELSIF state = ‘ 0 ’ THEN delay := 3 ns; ELSE delay := 4 ns; END IF; q <= state AFTER delay; EN ...

78 Chapter Four and all of the instances of the constant value are updated to reflect the new value of the constant. A constant ...

Data Types 79 Enumerated Real Integer Physical Scalar Array Record Composite File Access Figure 4-1 Types VHDL Data Types Diagra ...

80 Chapter Four to be a scalar type can hold, at most, one of the scalar values at any point in time. Referencing the name of th ...

Data Types 81 for the assignment to take place, either the base types must match or a type-casting operation must be performed. ...