Final Examination Fall 2002

PwnHero Ryerson University Department of Electrical and Computer Engineering ELE 538 – Microprocessor Systems Final Examination December 6, 2002 Time: 3 hours Closed book except for 68HC11 Technical Data and/or Reference book (Pink Book). Answer all questions in exam booklet. Use standard symbolic names for any internal registers. 1. (5 marks) Given the instruction sequence: ldaa #$60 adda #$80 adda #$30 Assuming that the Condition Code register was initially 0, what are the values of the N, Z, V and C bits after each of the three instructions are executed? 2. (10 marks) A system uses the Timer Output Compare registers 3 for timing operations. The system is to be set up so that bit 5 of Port A will output a pulse train that is “1” for 1000 microseconds and “0” for 2000 microseconds. The pulse train repeats indefinitely. Assume that the E-clock is 1 MHz. - Write initialization code in assembler to set up the proper registers, interrupt vector and any global variables you need. - Write the interrupt service routine. 3. ( 6 marks) Write assembly language code to modify Accumulator A so that the most significant bit is inverted, the least significant bit is cleared to ‘0’ and all other bits are set to ‘1’. (For example, if the initial contents were 111011, they would become 01111110) How many bytes does your machine language code occupy and how many clock cycles are required to execute it? (Note: full marks only if your solution is optimal.) 4. (12 marks) Three devices are to be mapped into the address space of a 68HC11 computer system: an 8K EPROM, an 8 bit output port occupying one memory address, and 4K of external RAM. - The internal RAM is mapped by the 68HC11 memory decoding circuitry to the memory region $0000 to $00FF. - Internal devices are mapped to the memory region $1000 to $103F. - No other devices will ever be added to this system, so memory should be “wasted” where pos- sible to simplify address decoding circuitry. The device must not cause a bus address conflict. (a) Draw a suitable memory map for the system, showing the location of the EPROM, output port and internal RAM. (b) Write the equations to select the output port, EPROM and external RAM. PwnHero.com