Addressing Modes

Question 1

LC-3 support 5 addressing nodes:

Answer 1

1. Immediate - the operand is encoded right into the instruction (constraints)
   
   1. EG. ADD R0,R1,#-4
2. Register - the operand is a register
   
   1. add R0,R1,R2
3. Direct (or PC relative) - located in memory where the EA is encoded in the instruction
   
   1. LD R1,Data
   2. EA = (PC) + sext(IR[8:0])
4. Indirect - located in memory where a pointer to the EA is encoded in the instruction
   
   1. LDI R1, Data - this loads into register r1 the content at the memory location stored at memory location data
5. Relative (Base+offset) located in memory a pointer to the EA is stored in a register.
   
   1. LDR R4,R5 #30