== Disc Information block ==
The "Disc Information block" is always at offset 0 in the disk image file. If track data exists, then this will immediatly immediately follow the Disc Information Block and will start at offset &100 in the disc image file.
The "Disc Information block" has the following structure:
*"number of sectors" is used to identify the number of valid entries in the sector information list.
*"sector size" parameter is used to calculate the location of each sector's data. Therefore, The data allocated for each sector must be the same. If the track contains different sized sectors, then the data allocated must be the size of the biggest sector. The "sector size" parameter is used to calculate the location of the sector data. Note that sector size's unit is 256-bytes. So, a sector size of 2, translates to 256 << (2-1), or 512 bytes.
*Sector data always follows Track Information Block at offset &100 from the start of the track information block.
*Sector data is stored in the same order as the sectors in the sector info block.
**b0 MA (Missing Address Mark)
*The following bits are used from NEC765 status register 2:
**b5 b6 CM (Control Mark)
**b5 DD (Data Error in Data field)
**b0 MD (Missing address Mark in Data field)
! Actual rate
|-
| 4Mhz 4MHz
| FM
| 4us 4µs per bit
|-
| 4Mhz 4MHz
| MFM
| 2us 2µs per bit
|}