
W83877TF
Publication Release Date: March 1998
- 14 -
Version 0.61
1.4 FDC Interface
SYMBOL
WE
DIR
PIN
85
89
I/O
OD
24
OD
24
FUNCTION
Write enable. An open drain output.
Direction of the head step motor. An open drain output.
Logic 1 = outward motion
Logic 0 = inward motion
Head select. This open drain output determines which disk drive
head is active.
Logic 1 = side 0
Logic 0 = side 1
Reduced write current. This signal can be used on two-speed
disk drives to select the transfer rate. An open drain output.
Logic 0 = 250 Kb/s
Logic 1 = 500 Kb/s
When bit 5 of CR9 (EN3MODE) is set to high, the three-mode
FDD function is enabled, and the pin will have a different
definition. Refer to the EN3MODE bit in CR9.
Write data. This logic low open drain writes precompensation
serial data to the selected FDD. An open drain output.
Step output pulses. This active low open drain output produces a
pulse to move the head to another track.
This schmitt input from the disk drive is active low when the
head is positioned over the beginning of a track marked by an
index hole. This input pin is pulled up internally by an
approximately 1K ohm resistor. The resistor can be disabled by
bit 4 of CR6 (FIPURDWN).
Track 0. This schmitt input from the disk drive is active low when
the head is positioned over the outermost track. This input pin is
pulled up internally by an approximately 1K ohm resistor. The
resistor can be disabled by bit 4 of CR6 (FIPURDWN).
HEAD
88
OD
24
RWC
87
OD
24
WD
86
OD
24
STEP
82
OD
24
INDEX
81
IN
cs
TRAK0
78
IN
cs
WP
77
IN
cs
Write protected. This active low schmitt input from the disk drive
indicates that the diskette is write-protected. This input pin is
pulled up internally by an approximately 1K ohm resistor. The
resistor can be disabled by bit 4 of CR6 (FIPURDWN).
RDATA
74
IN
cs
The read data input signal from the FDD. This input pin is pulled
up internally by an approximately 1K ohm resistor. The resistor
can be disabled by bit 4 of CR6 (FIPURDWN).
DSKCHG
76
IN
cs
Diskette change. This signal is active low at power on and
whenever the diskette is removed. This input pin is pulled up
internally by an approximately 1K ohm resistor. The resistor can
be disabled by bit 4 of CR6 (FIPURDWN).