20. 20. Combine the flowcharts that appear in Figures 4.11 and 4.12 so that the interrupt checking appears at a suitable place. Start Copy the PC to the MAR Copy the contents of memory at address MAR to IR; Increment PC by 1 Decode the instruction and place bits IR[11-0] in MAR Yes Instruction No requires operand? Copy the contents of memory at address MAR to MBR Execute the instruction FIGURE 4.11 The Fetch- Decode-Execute Cycle Yes Process the interrupt Has an interrupt been issued? No Perform fetch- decode-execute cycle FIGURE 4.12 Fetch-Decode-Execute Cycle with Interrupt Checking