CLEAR - Deleting a sector on the floppy disk

Syntax:

CALL 4014H
Input:

  • The corresponding drive must be switched on.

  • SCTR (IY+17) = Sector Number

  • TRCK (IY+18) = Track Number

Exit:

The addressed sector is physically erased from the disk.

Registers used:

AF, BC. DE, HL

Error handling:

In the event of an error, this routine automatically branches to the ERROR routine.Custom error handling is not possible.

The sector addressed in the DOS vectors SCTR (IY+17) and TRCK (IY+18) is physically erased on the diskette, i.e. overwritten with binary zeros (X’00’).

Note that you have to take care of switching the drive on and off yourself.

Before erasing the sector, make sure the disk is not write-protected.

Example:

...
DI                  ; disable interrupts
LD A,80H            ; select Drive 2
LD (IY+11),A
CALL 4008H          ; and turn on
LD BC,50            ; 50 ms delay
CALL 4038H
IN A,(13H)          ; check write protection
OR A
LD A,4
JP M,400EH          ; read only!
LD (IY+17),12       ; set Sector Number
LD (IY+18),28       ; set Track Number
CALL 4014H          ; erase sector
CALL 400BH          ; turn off drive
EI                  ; enable interrupts again
...

Sector 12 in track 28 of the disk in drive 2 will be erased.

Internally called routines: WRITE