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3.2
ELECTRICAL INTERFACE
Thi.s section gives a description of the signal levels, the
dri.ver/receiver
circuits,
and
the
interface
lines
of
the
FDl165.
3.2.1
Signal Levels
The input and output signals are at TTL levels and have the
following electrical specifications.
True
=
Logic 0 (low level), 0 to +0.4 Vdc
False
=
Logic 1 (high level), +2.5 to +5.25 Vdc
3.2.2
Driver/Receiver Circuits
Each driver circuit delivers a signal, on an interface line,
to the controller from the disk drive.
All driver circuits
are
the open-collector
type of
SN7438
Integrated Circuit
(Ie).
The SN7438 driver circuits sink a maximum current of
40 rnA at the low level.
Each receiver circuit receives a drive signal from the con-
troller.
The receiver circuits are Large Scale Integration
(LSI)
gate circuits that terminate with l50-ohm resistors.
Li nes recei ving at high speeds use a Schmi tt tr igger ga te.
Figure 3-1 shows the recommended driver/ receiver circuits.
CONTROLLER
MAXIMUM CABLE LENGTH
TWISTED PAIR 6 m
FLAT R.IBBON 3 m
DISK DRIVE
+5 V
SN7438 OR EQUIVALENT
SN7438 OR EQUIVALENT
I
I
HIGH SPEED LINE
~A
;h
I \
D
Figure 3-1
Driver/Receiver Circuits
3-2
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