W83877ATF Datasheet, PDF (19/191 Pages) Winbond – enhanced version from Winbonds most popular I/O chip W83877F

W83877ATF
1.4 FDC interface, continued
SYMBOL PIN
I/O
INDEX
81
IN_cs
MOA
MOB
STEP
DSA
DSB
WE
WD
RWC
79
OD₂₄
80
OD₂₄
82
OD₂₄
83
OD₂₄
84
OD₂₄
85
OD₂₄
86
OD₂₄
87
OD₂₄
HEAD
88
OD₂₄
DIR
VDD
GND
89
OD₂₄
15,
56
25,
40
65,
90
FUNCTION
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).
Motor A On. When set to 0, this pin enables disk drive 0. This is
an open drain output.
Motor B On. When set to 0, this pin enables disk drive 1. This is
an open drain output.
Step output pulses. This active low open drain output produces a
pulse to move the head to another track.
Drive Select A. When set to 0, this pin enables disk drive A. This
is an open drain output.
Drive Select B. When set to 0, this pin enables disk drive B. This
is an open drain output.
Write enable. An open drain output.
Write data. This logic low open drain writes precompensation
serial data to the selected FDD. An open drain output.
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.
Head select. This open drain output determines which disk drive
head is active.
Logic 1 = side 0
Logic 0 = side 1
Direction of the head step motor. An open drain output.
Logic 1 = outward motion
Logic 0 = inward motion
+5 power supply for the digital circuitry
Ground
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Publication Release Date: April 1998
Version 0.51