
W83977TF
PRELIMINARY
Publication Release Date: April 1998
-14-
Revision 0.62
1.5 Multi-Mode Parallel Port, continued
SYMBOL
PD7
PIN
23
I/O
I/O
24t
FUNCTION
-
OD
24
PRINTER MODE: PD7
Parallel port data bus bit 7. Refer to description of the parallel port
for definition of this pin in ECP and EPP mode.
EXTENSION FDD MODE: This pin is a tri-state output.
EXTENSION 2FDD MODE: DSA2
This pin is for Extension FDD A; its function is the same as the
DSA
pin of FDC.
1.6 FDC Interface
SYMBOL
PIN
I/O
FUNCTION
DRVDEN0
2
OD
24
OD
24
IO
24t
Drive Density Select bit 0.
DRVDEN1
GP10
3
Drive Density Select bit 1. (CR2A bit 1_0 = 00, default)
General purpose I/O port 1 bit 0. (CR2A bit 1_0 = 01)
(IRQIN1)
Alternate Function from GP10: Interrupt channel input.
P12
IO
24t
OUT
12t
KBC P12 I/O port. (CR2A bit 1_0 = 10)
SCI
System Control Interrupt (CR2A bit 1_0 = 11)
HEAD
5
OD
24
Head select. This open drain output determines which disk drive
head is active.
Logic 1 = side 0
Logic 0 = side 1
WE
9
OD
24
Write enable. An open drain output.
WD
10
OD
24
Write data. This logic low open drain writes pre-compensation
serial data to the selected FDD. An open drain output.
STEP
11
OD
24
Step output pulses. This active low open drain output produces a
pulse to move the head to another track.
DIR
12
OD
24
Direction of the head step motor. An open drain output.
Logic 1 = outward motion
Logic 0 = inward motion
MOB
13
OD
24
Motor B On. When set to 0, this pin enables disk drive 1. This is
an open drain output.
DSA
14
OD
24
Drive Select A. When set to 0, this pin enables disk drive A. This
is an open drain output.
DSB
15
OD
24
Drive Select B. When set to 0, this pin enables disk drive B. This
is an open drain output.