On most general purpose CPUs since the '70s, addresses are byte addresses.
This includes 6800, 680X0, PowerPC, x86, ARM, MIPS, SPARC, SuperH, Z80, PA-RISC...
- There are sometimes exceptions with DSPs that are not meant for processing bytes. (example : Analog Devices SHARC)
- Some small embedded CPUs may also have different addressing, or separate address spaces for instructions (example : Microsemi PIC)
- Some CPU support address spaces where data is aliased and expanded. For example mapping each bit at a different byte address (example : Some ARMs)
The actual width of the data bus is not directly related to the CPU internal architecture, wether it is a 8bits, 16bits or 32bits CPU.
- The MC68008 was a 16/32bits CPU with a 8 bits bus.
- The G3/G4 PowerPCs (PPC603, MPC755, MPC7450...) are 32bits CPUs with a 64bits data bus.
With a 32bits CPU, aligned 32bits word adresses are 0000_0000, 0000_0004, 000_0008 ... to ... FFFF_FFF0, FFFF_FFF4, FFFF_FFF8, FFFF_FFFC.
Some CPUs can do unaligned accesses, usually slower than aligned ones. An example : x86.
In that case, you could access a 32bits value at address 0000_0001.