External memory, the data bus and the address bus in ARM

Introduction

Address bus

Address bus connects to part of memory. setting the address bus to x will allow accessing ram at x.

Data bus

Data bus reads or writes to memory at location of address bus.

eg if loading byte of ram at position \(\#FF00\) to accumulator, address bus is \(\#FF00\).

using RAM: LDR and STR str r0, [r1] store value in r0 at memory location indicated by r1 ldr r0, [r1] load value at r1 in memory to r0 ldr r0, [r1, #4] load value at r1 offset by 4 to r0