Page processing sequence:
- Repeat with buffer 0 to S-1
- 512-byte data, processing ON
- One time with buffer 0
- size0 nibbles spare, processing ON
- Repeat with buffer 0 to S-1
- 1 nibble padding spare, processing OFF
- size1 nibbles spare, processing ON
Checksum: Spare area size (nibbles) = size0 + (S – (1 + size1))