Midterm Solutions Fall 2003

PwnHero 1. In Fig.1, a common-cathode seven-segment display is driven by port B. (Note: Solutions are in Bold Letters) Buffer PB7 PB6 PB5 PB4 PB3 PB2 PB1 a b c d e f g common cathode a b c d e f g 68HC11 Figure 1. 100 : each PB0 Not used (a) Show the hex values required to reproduce the following 3 patterns on this display: (C6; FA; 1E) (b) Modify the following program so that the number on the seven-segment changes from 0 to A and then stops PORTB EQU $1004 ORG $6000 CLRB LOOP LDX #DIS ABX LDAA 0,X STAA PORTB CMPA #$A BEQ DONE JSR TIMDEL INCB ANDB #$0F BRA LOOP DONE SWI TIMDEL PSHY LDY #57140 LOOP DEY BNE LOOP PULY RTS DIS FCB $FC,$60,$DA,$F2,$66,$B6,$BE,$E0 FCB $FE,$F6,$EE,$3E,$9C,$7A,$9E,$8E 2. Take the contents of address $0020, toggle the least significant 4 bits of this value, LDAA $20 and store the result in address $0021. EORA #$0F STAA $21 3. Enter the ASSEMBLY LANGUAGE instructions in the chart below that corresponds to the comments in the chart. Remember to start your program at HEX Address 0100. PwnHero.com