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3. 7
FLOPPY DISK DRIVE CONTROL
The Floppy Disk Drive Controller uses a mlnlmum of
hardware and requires a sophisticated program,
implemented in ROM, to read from and write to the disk
drives. Some of the timing and motor control is
determined by the program.
The
program communicates with
the Floppy Disk
Controller in the following ways:
1. Through the Shared I/O Interface registers described
in Section 3.4.
2.
By outputting control bytes to the Drive Control
register. The format for the register is shown in
Table
3-16,
and its I/O address is listed in Table
3-15.
3. By accessing the other I/O addresses given in Table
3-15.
Table 3-15
Floppy Disk I/O Addresses
I/O Address
(Hexadecimal)
Operation
Description
80
INPUT
so
OUTPUT
ADVANTAGE
Input Disk Data. Sets the processor
into
the
wait state
until
the
disk
data
is
available,
then
reads
the data.
Inputting
from
this
address
when
data
is
unavailable
puts
the
processor
into a continuous wait state.
Output Disk Data. Sets the processor
into the wait state until the Disk
Controller writes the data to the
diskette.
Outputting
to
this
address
before setting the
Disk
Write
flag
puts
the
processor
into a continuous wait state.
3-31
TECHNICAL MANUAL
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