Z80 Assembly 43: Memory Banking (Switching ROM and RAM)
The Limitation: 64 KB Address Space The Z80 uses 16-bit address lines, meaning it can only directly address 64 kilobytes (65,536 bytes) of memory (from address 0000H to FFFFH). Since many systems (like the MSX or larger Spectrums) have $128$ KB or more of RAM/ROM, they must use Memory Banking to access it all. How Memory Banking Works Memory Banking is the technique of using an I/O port to physically switch which $16$ KB or $8$ KB block of memory is visible to the CPU at a specific address range. ...