Lecture 12 Objectives

KNOW:

• The JMP and TRAP instructions of the LC-3

BE ABLE TO:

• Use a TRAP to do I/O
• Write an LC-3 machine code program that does looping and I/O
• Explain how specific instructions affect the LC-3 Data Path (Fig. 5-18 in the textbook)

Sample Exam Question:

When a JMP execution is executed, the signal GatePC will be enabled (i.e. JMP causes a new value to be loaded into the PC, which is then made available to MAR via the system bus). Looking at the diagram of the LC-3 data path, identify which inputs from the muxes controlled by ADDR2MUX and ADDR1MUX will be fed into the adder that calculates the new PC value, during the execution of a JMP instruction.