| Bits | Description |
|---|---|
| 7 | 1 to select bank 7, 0 to select bank 5 |
| 6 | Reserved, must be 0 |
| 5:0 | MSB of address of the tilemap in Bank 5 |
The value written into bits 5:0 is an offset into 16K bank 5 or 8K bank 7 allowing the tilemap to be placed at any multiple of 256 bytes. The value written here can be thought of as the MSB of an address in bank 5 0x40-0x7f or bank 7 0xc0-0xff. Because bank 7 is only 8K in size, addresses wrap across the 8K boundary instead of the 16K boundary.