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DUST COVER
The design of an enclosure should incorporate
a means to prevent contamination from loose
items, e.g., dust, lint, and paper chad since the
drive does not have a dust cover.
COOLING
Heat dissipation from a single drive is nor-
mally 20 watts, 68 BTU per hour, under high
load conditions. When the drive is mounted so
the components have access to a free flow of
air, normal convection cooling allows opera-
tion within the specified temperature range.
When the drive is mounted in a confined
environment, air flow must be provided to
maintain specified air temperatures in the
vicinity of the motors, printed circuit boards,
and diskettes.
When forced air is used, air flow must be
directed outward from the drive. Do not
intake air through the drive or heads and
diskettes.
3.4 INTERFACE CONNECTIONS
Interface connections for the TM848-1E and
TM848-2E are made via a user-supplied, fifty-
pin, flat ribbon connector, 3M Scotchflex, Part
Number 3415, or its equivalent. This connec-
tor mates directly with the circuit board
connector at the rear of the drive.
The interface description of the connectors,
and the location of each one, is contained in
this section. Interface lines are located in
Table 3-1. D. C. power connector pin assign-
ments are located in Table 3-2, Section 3.5 of
this manual.
The signal wire harness should be of the flat
ribbon or twisted pair type, have a maximum
length of ten feet, and have a 26-to-28 gauge
conductor compatible with the connector to be
used. It is recommended that the interface
cable have a characteristic impedance of 100
ohms.
3-2
All interface signals are TTL compatible.
Logic true (low) is +0.4 volt maximum. Logic
false (high) is + 2.4 volts minimum.
INPUT CONTROL LINES
These input lines are individually terminated
through a 150 ohm resistor pack installed in
the dip socket located at integrated circuit
location RP5 (or RP1 in the Large Scale Inte-
gration version). In a single-drive system, this
resistor pack should be installed to provide
the proper terminations. In a multiple-drive
system, only the last drive on the interface is
to be terminated. All other drives on ,the inter-
face must have the resistor pack removed.
The drive can terminate the following input
lines:
1. Direction
2. Step
3. Write Data
4. Write Gate
5. In Use
6. Side Select (TM848-2E only)
7. Write Current Switch
8. Head Load
MOTOR ON CONTROL
The Motor On Control lines are used to control
the spindle motor. With the MOL jumper in
(factory installed), the Motor On Control lines
are low true. With the MOH jumper installed
(optionaD, the Motor On Control lines are
high true (see Table 3-3 located in Section 3.6).
DRIVE SELECT LINES
The Drive Select lines provide a means of
selecting and deselecting a drive. These four
lines, DS1 through DS4, allow independent
selection of up to four drives attached to the
controller.
When the signal logic level is true (low), the
drive electronics are activated, and the drive
is conditioned to respond to Step or to Read/
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