memory addressing

Complete

Summary

Endianness

Big-endian -> most significant byte in lowest address
Little-endian -> least significant byte in lowest address

affects the order of bytes within a multi-byte word, within the byte nothing changes

Register addressing

R-type
operand is specified in registers

Immediate addressing

I-type
operand is specified in the instruction

Displacement addressing

I-type - load/store
operand is in memory

Concept

Addressing modes

ways to specify an operand

Addressing mode	Example	Meaning
Register	`add r1, r2`	`r1 <- r1 + r2`
Immediate	`add r1, 3`	`r1 <- r1 + 3`
Displacement	`add r1, 8(r2)`	`r1 <- r1 + mem[r2+8]`
Register indirect	`add r1, (r2)`	`r1 <- r1 + mem[r2]`
Indexed/Base	`add r1, (r2+r3)`	`r1 <- r1 + mem[r2+r3]`
Direct/Absolute	`add r1, (100)`	`r1 <- r1 + mem[100]`
Memory indirect	`add r1, @(r2)`	`r1 <- r1 + mem[mem[r2]]`
Auto-increment	`add r1, (r2)+`	`r1 <- r1 + mem[r2]` `r2 <- r2 + x`
Auto-decrement	`add r1, -(r2)`	`r2 <- r2 - x` `r1 <- r1 + mem[r2]`
Scaled	`add r1, 100(r2)[r3]`	`r1 <- r1 + mem[100+r2+r3*x]`