Module Title: Microprocessor Systems 2

Transcription

1 CORK INSTITUTE OF TECHNOLOGY INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ Autumn Examinations 2008/09 Module Title: Microprocessor Systems 2 Module Code: ELTR6017 School: Electrical and Electronic Engineering Programme Title: Bachelor of Engineering in Electronic Engineering Stage 2 Programme Code: EELXE_7_Y2 External Examiner(s): Mr D Denieffe Dr P O Sullivan Internal Examiner(s): Mr J O Sullivan Instructions: Attempt any three questions. All questions carry equal marks. Ensure you return the before-and-after sheet with your answer book. Duration: Two hours Sitting: Autumn 2009 Requirements for this examination: N/A Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the correct examination paper. If in doubt please contact an Invigilator. You are expected to present your answers in a neat and tidy fashion Start each question on a new page Remember that there is plenty of time two hours to do three questions

2 Q1 (a) Briefly explain what is meant by a subroutine and describe how subroutines are facilitated in a microcomputer. (b) The subroutine below is a programmer s first effort at writing a subroutine to generate a short delay on the Flight-68K microcomputer development system. The code contains a fatal error. Identify the error, explain its effect and show how the subroutine could be rewritten to rectify the mistake. DELAY MOVE.L #25000,D0 SUB.L #1,D0 BNE DELAY RTS (c) Assuming the master clock on the Flight-68K operates at a frequency of 10MHz and the execution times for the instructions SUB.L and BNE are 12 and 8 MPU cycles respectively, determine the length of the delay generated by the above subroutine, when fixed show all working. (d) Write a main program which uses the above subroutine to slowly print out on the Flight-68K system a welcome message stored as a NULL-terminated ASCII string at location $ Use system subroutine OUTCH to facilitate printing of the message. [3 marks] [6 marks] [6 marks] Q2 (a) Draw a simplified block diagram showing the internal structure of a programmable 8-bit single-port parallel input/output chip, and describe the function of each section of the device. How is the MPU able to access each section of this chip? (b) Use a circuit diagram to show how four switches and four LEDs could be interfaced to the parallel port of the above chip. Give a brief explanation of the circuit action. (c) With the aid of a simple diagram, explain how the input/output port lines can be configured for the above setup, and write a sample instruction that would facilitate this. (d) Complete the before-and-after table accompanying this paper. [3 marks] [8 marks] Microprocessor Systems Cork Institute of Technology

3 Q3 Figure 2 below shows a section of memory in a based computer. Carefully analyse this circuit and answer the following questions. In each case give reasons for your answer and where appropriate, show any calculations or other relevant working. (a) Are the memory chips in the diagram, RAM or ROM?. (b) Determine the capacity of each chip. (c) What data is stored in (i) the chip on the left, (ii) the chip on the right? (d) Using a truth table, explain in detail the function performed by the two-input NAND gates in the centre of the circuit. (e) Explain the purpose of the nine-input NAND gate on the right to which address lines A23 - A16 are connected. (f) Using an address map, determine the range of addresses occupied by the pair of memory chips in the circuit. (g) What is the purpose of the delay circuit near the MPU? (h) Describe the sequence of action that takes place when the MPU reads a word of data from this memory, paying particular attention to all control lines shown. [2 marks] [2 marks] A23 A15 A15 A16 A1 AS LDS UDS 16-bit MPU (68000) CS CS MEN DTACK Delay circuit D15 D8 D7 D0 Figure 2 Microprocessor Systems Cork Institute of Technology

4 Q4 (a) In relation to serial data communications, what do the letters UART stand for? (b) With the aid of a diagram, explain the principle of asynchronous serial datacommunications, and describe how the receiving computer is able to maintain synchronism with the incoming data stream. (c) Figure 1 below shows how an MC68681 DUART chip might be connected to a MPU. Carefully analyse the diagram and answer the following questions: (i) identify and state the function of the chip (ii) describe the function of all lines on the right hand side of the chip. (iii) what is the purpose of address lines A1-A4 connected to the DUART? (iv) is the DUART an 8-bit or 16-bit device? - explain fully your conclusion (v) explain the function of the crystal connected to the X1 and X2 inputs. [10 marks] A5-A23 A1-A4 A1-A23 RS1-RS4 TXDA MC68000 MPU AS LDS Address decoder SEN CS X1 MC68681 DUART RXDA IP0-IP5 X2 OP0-OP7 RESET DTACK RESET DTACK TXDB D0-D15 D0-D7 RXDB D0-D15 D0-D7 Figure 1 (d) Table 1 below shows a subroutine called INCH, written to input a character via Port A of the DUART. In relation to the overall task being performed, explain the function of each line of the routine. N.B see extra data on next page INCH MOVEA.L #$A00001,A0 WAIT MOVE.B 2(A0),D0 LSR.B #1,D0 BCC WAIT MOVE.B 6(A0),D0 RTS Table 1 Microprocessor Systems Cork Institute of Technology

5 The following information from the Flight-68K manual may be of help to you: DUART base address: $A00001 Port A status register: $A00003 Port A Rx buffer register: $A00007 Port A Status Register SRA Break Frame Parity Overrun TxEMT TxRDY FFULL RxRDY Microprocessor Systems Cork Institute of Technology

6 CORK INSTITUTE OF TECHNOLOGY INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ Semester 2 Examinations 2008/09 Module Title: Microprocessor Systems 2 BEFORE-AND-AFTER TABLE Question 2(d) Registers before Flags before Instruction Registers after Flags after D0: D1: MOVE.B D1,D0 D0: D1: D0: 19A42B6A D1: B72D CMP.B D0,D1 D0: D1: D0: 7125BA9C EOR.B #$0F,D0 D0: D0: 41D ROR.B #2,D0 D0: Name: Return this sheet with your answer book Microprocessor Systems Cork Institute of Technology