NEC FD1165 - 3.2 Electrical Interface

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