ACT apricot - Sector Register; Status Register; Track Register

FLOPPY DISK INTERFACE
command currently in progress is indicated by an associated
control
bit within the Status Register.
The eleven commands can be divided into four different
categories as detailed below. A detailed description of
each
command is provided in the PROGRAMMING
CONSIDERATIONS section.
Type 1. Readlwrite head positioning commands:
Restore, Seek, Step, Step-in, Step-out.
Type 2. Data transfer commands: Read Sector, Write
Sector.
Type 3. Format code transfer commands: Read Address,
Read Track,
Write Track.
Type 4. Interrupt command: Force Interrupt.
Status Register
The 8-bit Status Register holds status information, which
is dependent on the command operation performed by the
FDC. The register is located at address 40H in the system
1/0 space, and can only be read from. Some of the bits
within the register signify the state of the control inputs
from the disk drive, whilst others indicate the status of the
command operation.
Track Register
The 8-bit Track Register indicates the track number of
the position of the drive readlwrite head and is located at
address location 42H in the system 1/0 space. The register
can be
written to and read from. The FDC updates the track
register during head positioning command operations, every
time the drive head is moved to an adjacent track.
Sector Register
The 8-bit Sector Register is used to store a sector number,
which indicates to the FDC the desired location on the disk
for a transfer operation.
The register is located at address