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2.4.2.1
Terminator Resistors
All disk drives are shipped with terminator resistor arrays
(RNI and RN2) installed as shown in Figure 2-3.
Do not re-
move these resistors when only a single disk drive is used
in a system.
Do not remove these resistors when two or more disk drives
are served by a single controller but are connected in par-
allel as shown by (A) in Figure 2-4.
However, if two or
more disk drives are connected to the controller on a common
line in series (daisy chain) as shown in
(B)
of Figure 2-4,
remove RNI and RN2 from each disk drive except the last one
in the circuit.
2.4.2.2
Drive Identification Selection (OX)
When only one dfLsk drive is used in a system, insert the
DRIVE SELECTION shorting plug (see Figure 2-3) to identify
that dr ive as DXI.
When two or more disk dr ives are used
in a system (four maximum), assign each one a different OX
number and insert the shorting plug for that unit appropri-
ately
(see Figure 2-3).
The unit
is
supplied with DXI
selected.
2.4.2.3
Option Selection
The
following
section describes
option selection on the
FDl165
PCB.
See Figure 2-3 for the location of the selec-
tion plugs and pins and a configuration chart.
See Chapter
3 for an explanation of the signals.
HEAD LOAD PLUG (HL)
When you select plug position 1, head load action is initi-
a ted by a Head
r..
oad signal f rom the con troller.
When you
select plug position 2, head load action is initiated by a
Drive Select signal from the controller.
The unit is sup-
plied with HL
1
selected.
RADIAL READY PLUG (RX)
When you select plug position 1, the Ready signal sent from
the disk drive i.s gated by the Drive Select signal.
When
you select plug position 2, the Ready signal is independent
of the drive select signal.
The unit is supplied with RX 1
selected.
2-5
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