FLOPPY DISK CONTROLLER INTERNAL
REGISTERS
FLOPPY DISK CONTROLLER
The Floppy Disk Controller (FDC) provides the
interface between a host microprocessor and
the floppy disk drives. The FDC integrates the
functions of the Formatter/Controller, Digital
Data Separator, Write Precompensation and
Data Rate Selection logic for an IBM XT/AT
compatible FDC. The true CMOS 765B core
guarantees 100% IBM PC XT/AT compatibility
in addition to providing data overflow and
underflow protection.
The Floppy Disk Controller contains eight
internal registers which facilitate the interfacing
between the host microprocessor and the disk
drive. Table 2 shows the addresses required to
access these registers. Registers other than the
ones shown are not supported. The rest of the
FDC description assumes the Base I/O Address
is 3F0.
The FDC37C669 is
compatible
to
the
82077AA using SMSC's proprietary floppy disk
controller core.
Table 2 - Status, Data and Control Registers
BASE I/O
ADDRESS
REGISTER
+0
+1
+2
+3
+4
+4
+5
+6
+7
+7
R
R
Status Register A
SRA
SRB
DOR
TSR
MSR
DSR
FIFO
Status Register B
R/W
R/W
R
Digital Output Register
Tape Drive Register
Main Status Register
Data Rate Select Register
Data (FIFO)
W
R/W
Reserved
R
Digital Input Register
Configuration Control Register
DIR
W
CCR
For information on the floppy disk on Parallel Port pins, refer to Configuration Register CR4
and Parallel Port Floppy Disk Controller description.
18
SMSC [ SMSC CORPORATION ]
