ECE 511: Digital System & Microprocessor

1. ECE 511: Digital System & Microprocessor

2. Week Subject W1 Digital Logic Review W2-W3 Microprocessor Architecture & Overview W3-W6 Microprocessor Instruction Set & Programming W7-W9 Memory Interfacing W10-W12 Parallel I/O Interfacing Course Outline

3. References • J. L. Antonakos, “The 68000 Microprocessor: Hardware and Software Principles & Applications,” 5th Ed., Pearson Prentice-Hall, 2004. • C. M. Gilmore, “Microprocessors: Principles & Applications,” 2nd Ed., McGraw-Hill, 1995. • A. Clements, “Microprocessor System Design,” PWS-Kent, 1992.

4. Course Evaluation • Tests x 2 30% • Quizzes x 3 20% • Mini Projects 50%

5. If you have problems, please contact me: Ahmad Ihsan bin Mohd Yassin Rm. T2-A13-1A, Dept. of Comp. Eng. Faculty of Elect. Eng. UiTM, Shah Alam. 03-55436118, 017-2576295 *Please call before you see me.

6. Digital Logic Review: Part I ECE 511: Digital System & Microprocessor.

7. What we will learn in this session: • Review of logic gates. • Flip-flops. • Decoders. • Universal representation of logic gates.

8. Gates

9. What are gates? • Gates are: • Simple electronic devices. • Constructed using transistors. • Used to design digital systems. • Three Basic Gates: • AND • OR • NOT • Basic Gates can be combined into Extended Gates. • Usually packed into ICs.

10. Gates as Building Blocks

11. A C AND B TRUTH TABLE A B C 0 0 0 1 0 0 0 0 1 1 1 1 Basic Gate - AND • The AND gate is similar to multiply operation.

12. A OR C B TRUTH TABLE A B C 0 0 0 1 1 0 1 0 1 1 1 1 Basic Gate - OR • The OR gate is similar to add operation.

13. TRUTH TABLE A B 0 1 NOT A B 1 0 Basic Gate - NOT • The NOT gate performs the inverse operation.

14. Extended Gates • Combination of basic gates to perform complex functions: • NAND • NOR • XOR • XNOR • Flip-Flops

15. TRUTH TABLE A B C 0 1 0 1 1 0 1 0 1 A 1 1 0 A C NAND C NOT AND B B NAND Gate • Adds NOT after AND gate. • AND outputs are inverted  NAND (NOT-AND).

16. A A C OR NOT C NOR B B TRUTH TABLE A B C 0 1 0 1 0 0 0 0 1 1 1 0 NOR Gate • Adds NOT after OR gate. • OR outputs are inverted  NOR (NOT-OR).

17. A XOR C B TRUTH TABLE A B C 0 0 0 1 1 0 1 0 1 1 1 0 XOR Gate • XOR performs the Exclusive Or operation. • When A=B, C=0; when A≠B, C=1.

18. A XOR B TRUTH TABLE A B C 0 1 0 1 0 0 A 0 0 1 C XOR NOT C B 1 1 1 XNOR Gate • Adds NOT after XOR gate. • XOR outputs inverted  XNOR (NOT XOR).

19. Flip-Flops

20. Flip-Flops • An extended gate used as memory: • Each FF stores 1 bit. • 2 gates, feedback connections. • 2 inputs, 2 outputs. • More complex ones may: • Use timing from CLK. • Perform bit toggle.

21. Reset-Set (RS) Flip-Flop • 4 states: • Three stable (Set, Reset, and Keep). • One not stable (Unused). • 2 inputs, 2 outputs. • May also contain clock (CLK) signal.

22. RS Flip-Flop RSFF R Q *Assuming initial condition: S = 0, R = 0, Q = 0 S Q’ Qprev S R Q Q’ KEEP: Output unchanged N/A 0 0 0 1 SET: Output set (Q = 1) 0 1 0 1 0 RESET: Output reset (Q = 0) 1 0 1 0 1 *As long as S=0 and R=0, Q will always remain at previous state. Doesn’t matter 1 1 N/A N/A Unstable

23. Clocked RS Flip-Flop RSFF R Q *Assuming initial condition: S = 0, R = 0, Q = 0 CLK Qprev S R CLK Q Q’ S Q’ KEEP: Output unchanged N/A 0 0 ↑ 0 1 0 Doesn’t matter Doesn’t matter ↓ 0 1 Only active when CLK is ↑ SET: Output set (Q = 1) 0 1 0 ↑ 1 0 RESET: Output reset (Q = 0) 1 0 1 ↑ 0 1 Reduced sensitivity to noise. Doesn’t matter 1 1 ↑ N/A N/A Unstable

24. Qprev J K Q Q’ N/A 0 0 0 1 Output unchanged 0 1 0 1 0 Output set (Q = 1) 1 0 1 0 1 Output reset (Q = 0) Q 1 1 Q Q Toggle JK Flip-Flop • Same as RS, but forbidden state used to toggle bit. • Can also be clocked using CLK. *Assuming initial condition: J = 0, K = 0, Q = 0

25. Qprev S R Q Q’ N/A 0 0 0 1 Output unchanged 0 1 0 1 0 Output set (Q = 1) 1 0 1 0 1 Output reset (Q = 0) Q 1 1 Q Q Toggle JK Flip-Flop J Q K Q *Assuming initial condition: J = 0, K = 0, Q = 0

26. Clocked JK J Q CLK K Q Qprev S R CLK Q N/A 0 0 ↑ 0 Output unchanged 0 Doesn’t matter Doesn’t matter ↓ 0 Only active when CLK is ↑ 0 1 0 ↑ 1 Output set (Q = 1) 1 0 1 ↑ 0 Reduced sensitivity to noise. Output reset (Q = 0) Q 1 1 ↑ Q Toggle

27. D-Flip-Flop • Data latch. • Modification of RSFF. • Stores 1-bit of information. • Can be combined to store more. • Data are stored in memory using millions of DFFs.

28. D-Flip-Flop DFF D Q EN Q’ Qprev D EN Q Q’ QPREV Doesn’t Matter 0 QPREV Q’PREV *Only active when EN is 1 Doesn’t Matter 1 1 1 0 Output set (Q = 1) Doesn’t Matter 0 1 0 1 Output reset (Q = 0)

29. D-Flip-Flop: Timing Diagram D EN Q

30. Storing 8-bits using DFF (RAM) Data Bus D0 D1 D2 D3 D4 D5 D6 D7 DFF DFF DFF DFF DFF DFF DFF DFF EN Q0 Q1 Q2 Q3 Q4 Q5 Q6 Q7

31. Asynchronous Latch • Allows both synchronous & asynchronous operations: • Synchronous: CLK driven (Clocked JK). • Asynchronous: similar to RSFF. • 5 inputs, 2 outputs: • J, K and CLK for synch. operation. • PR, CLR for asynch. operation.

32. PRE(S) J Q PRE CLR Q CLK 0 0 Follows J, K, CLK (Synch. JK) K Q 0 1 Q = 0, resets output. 1 0 Q = 1, sets output. 1 1 Not valid. CLR(R) Asynchronous Latch

33. Universal Gates – NAND and NOR

34. NAND and NOR as Universal Gates • In industry, NAND and NOR gates are most common. • Reason? • Can be used to represent any gate (functionally complete). • Easiest & cheapest to produce.

35. NAND Logic

36. NAND Logic

37. NOR Logic

38. NOR Logic

39. IC 4011 IC 7402

40. Decoders

41. Decoder • A digital circuit that detects a specific combination of input bits (code), and indicates the presence of the code by a specific output. • Typically has n inputs and 2n outputs, but other combinations also exist. • However, the number of inputs is always less than the outputs (noInputs < noOutputs). • Each combination of inputs will generate a unique pattern at the output.

42. 2-4 Decoder Y0 I0 Y1 Y2 I1 Y3 Example: Active High 2-4 Decoder I1 I0 Y3 Y2 Y1 Y0 0 0 0 0 0 1 0 1 0 0 1 0 1 0 0 1 0 0 1 1 1 0 0 0 A specific pattern at the inputs. Will activate a specific bit at the outputs.

43. 2-4 Decoder Y’0 I0 Y’1 Y’2 I1 Y’3 Example: Active Low 2-4 Decoder I1 I0 Y’3 Y’2 Y’1 Y’0 0 0 1 1 1 0 0 1 1 1 0 1 1 0 1 0 1 1 1 1 0 1 1 1 A specific pattern at the inputs. Will activate a specific bit at the outputs.

44. Example: Active High 3-8 Decoder A B C Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 0 0 0 0 0 0 1 0 0 1 0 0 0 0 0 0 1 0 0 0 1 1 0 0 0 0 1 0 0 0 1 0 0 0 0 0 1 0 0 0 0 1 0 1 0 0 1 0 0 0 0 0 1 1 0 0 1 0 0 0 0 0 0 1 1 1 1 0 0 0 0 0 0 0

45. Example: Active Low 3-8 Decoder A B C Y7’ Y6’ Y5’ Y4’ Y3’ Y2’ Y1’ Y0’ 0 0 0 1 1 1 1 1 1 1 0 0 0 1 1 1 1 1 1 1 0 1 0 1 0 1 1 1 1 1 0 1 1 0 1 1 1 1 1 1 0 1 1 1 1 0 0 1 1 1 0 1 1 1 1 1 0 1 1 1 0 1 1 1 1 1 1 1 0 1 0 1 1 1 1 1 1 1 1 1 0 1 1 1 1 1 1 1

46. Encoder vs. Decoder 8  3 Encoder I0 I1 I2 Y2 I3 Y1 I4 Y0 I5 I6 I7 I0 I1 I2 I3 I4 I5 I6 I7 Y0 Y1 Y2 1 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0 0 1 0 0 0 0 0 0 1 0 0 0 0 1 0 0 0 0 0 1 1 0 0 0 0 1 0 0 0 1 0 0 0 0 0 0 0 1 0 0 1 0 1 0 0 0 0 0 0 1 0 1 1 0 0 0 0 0 0 0 0 1 1 1 1

47. Encoder vs. Decoder 3  8 Decoder I0 I1 Y2 I2 Y1 I3 Y0 I4 I5 I6 I7 Y0 Y1 Y2 I0 I1 I2 I3 I4 I5 I6 I7 0 0 0 0 0 0 0 0 0 0 1 0 0 1 0 0 0 0 0 0 1 0 0 1 0 0 0 0 0 0 1 0 0 0 1 1 0 0 0 0 1 0 0 0 1 0 0 0 0 0 1 0 0 0 0 1 0 1 0 0 1 0 0 0 0 0 1 1 0 0 1 0 0 0 0 0 0 1 1 1 1 0 0 0 0 0 0 0

48. Y0 I0 = Y0Y1Y2 Y1 I1 = Y0Y1Y2 I2 = Y0Y1Y2 Y2 I3 = Y0Y1Y2 I4 = Y0Y1Y2 I5 = Y0Y1Y2 I6 = Y0Y1Y2 I7 = Y0Y1Y2 What Goes on Inside a Decoder?

49. Decoders • In this subject, you need to familiarize yourself with two types of decoders: • 74LS139 Dual 2-4 Line Decoder. • 74LS138 3-8 Line Decoder • Decoders are used to: • Activate devices for use by µP. • Memory, I/O interfacing.

50. 74LS139 Dual 2-4 Line Decoder • Motorola active low 2-4 decoder. • 2 x decoders in one IC. • 16 pins total: • 2 x (2 inputs, 4 outputs). • Vcc (±5V) and GND. • 2 x Enable pins.