Hdl Lab Viva Questions

 HDL LAB VIVA QUESTIONS 

1. QUESTIONS related to Xilinx tool

1. What type of language is VHDL? 2. What is the basic building unit of a VHDL design? 3. What do all VHDL designs begin with? 4. Which block describes a design's interface? 5. Which block describes a design's behavior? 6. What is the difference between simulation and synthesis? 7. Which data type defines a single logic signal? 8. Which data type describes a bus? 9. What two ways can a vector's range be described? 10. What are the IEEE STD_LOGIC_1164 data types for single logic signals and buses? 11. Why is it desirable to use IEEE STD_LOGIC_1164 data typing? 12. What are the only two values for a Boolean type? 13. What are the numerical data types? 14. What is SUBTYPING used for? 15. What type is use to create a user data type? 16. What reserved word is used to declare a user data type? 17. Create the use data type DAYS and assign it the values: MON, TUE, WED, THU, FRI,SAT and SUN. 18. Which data type is used for a string of ASCII characters? 19. Which data type includes time units as values? 20 Create the entity block for a three input XOR gate. 21. Which symbol is used to end all VHDL statements? 22. What part of a port declaration defines signals in or out direction? 23. Which VHDL construct is used to define a literal constant in an entity block? 24. Create the integer constant included in an entity block called BUS_SIZE and assign it a value of 32. 25. Which symbols are used as an assignment operator to assign a literal to an identifier name?

26. What are the two primary ways to describe a logic circuits function within an architecture  block? 27. Create the architecture block for the 3-input XOR gate of question 21. 28. Which symbols are used to assign an expression's result to an output interface signal? 29. What are the rules used to define an identifier name? 30. What symbols define a comment line? 31. Write the statements that will allow a design to access all the contents of the IEEE ARITH. 32. Make the delay in question 33 transport rather than inertial. 33. How does a transport trans port delay differ from an inertial delay? de lay? 34. What is the purpose of a SIGNAL declaration? 35. Where are SIGNAL declarations placed in the design? 36. Write an assignment statement that assigns the contents of s(5) to t(2). 37.What is the purpose of a process' sensitivity list? 38 Under what conditions is a process run? 39 What is an EVENT? 40 What is the difference between event and non-event driven process execution? 41. Write a process block that keeps a running tally of each time an interrupt (INT) signal is asserted high. 42. Which symbols are used to differentiate between logic 1 and an integer 1? 43. What are the results of using CLK'event as a condition in the if statement of the DEF example? 44.In an if..then..else construct, which statements are executed if the condition is TRUE and which if it is FALSE? 45. What reserved word is used to nest if..then..else statements? 46. Write the process block that separately tallies positive and negative transitions of the signal TIME_OUT. 47. What is the purpose of a for loop? 48. What are the requirements for a for loop? 49. Write a process block th at uses a for loop to set a zero z ero flag high if all the bits b its in a sixteen (16) bit word are low (zero). 50. Write is the general rule for component declarations?

51. What is meant by instantiating a component? 52. How do s ignal declarations differ from port interface declarations? 53. What is the prime use of signals? 54. How many parameters can be passed into a function? 55. How many results can be returned from a function? 56. Write a function th that at returns the sum of two 8-bit words. 57. How are functions called? 58. How do procedures differ from functions? 59. Which standard library does not require a library or use statement? 60. What is a PACKAGE? 61. When is a PACKAGE BODY used? 62. What is the name of the library used by the current design to store compiled results? 63. Which standard library is used to access the keyboard and monitor screen?