Chapter 5: LC-3

What is the ISA? And what does it do?

Instruction Set Architecture - all of the programmer-visible components and operations of the computer

List 3 control instructions

JMP, BR, JSR, RTI, TRAP

What are conditions codes?

LC-3 has 3 condition codes: N,Z,P - set by any instruction that writes a value to a register

Give an example of PC-Relative Mode

LD and ST

List 3 Data Movement Instructions.

LD, LDI, LDR, LEA, ST, STI, STR

Give an example of Indirect Mode

LDI and STI

Give an example of Base + offset mode

LDR and STR

What is Addressability?

The number of bits stored in each memory location - 16 bits for LC-3

What is address space?

The total number of uniquely identifiable location as the memory's address space - 2^16 locations (16-bit addresses)

What are condition codes used for?

Used to change the execution sequence for some of the instructions

What is sign extension?

extend the first number of the code out to maintain the sign (because given a 5-bit code of instruction, it needs a 16-bit value for the ALU)

What addressing modes are supported by LC-3? (5 total)

1. PC-Relative (offset) 2. Indirect 3. Base + Offset 4. Immediate 5. Register

What are the three classes of instruction?

1.Computational/Operate Instructions 2. Data Movement Instructions 3. Control Instructions

How big is each register?

16-bits

How many bits is the instruction opcode?

4 bits

How many registers are in the LC-3

8 Registers

List 3 Computational/Operate Instructions

ADD, AND, NOT