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