Disk Drive Configuration - NorthStar HORIZON Manual

DISK DRIVE CONFIGURATION
If the HORIZON is to be configured with only one disk drive
connected to the controller then no modification is required for
the disk drive. If two or more drives are to be connected to the
controller then the following disk drive modifications must be
made. Note that when there are two disk drives mounted in the
HORIZON front panel, drive #1 should be on the left and drive #2
should be on the right. If a third or fourth drive is to be
connected, then drive #3 and drive #4 will be mounted outside of
the HORIZON chassis.
A. The drive number for each drive must be programmed using the
SJrogram shunt (located at IF) on the disk drive PC board. The
three metal straps labeled OSl, OS2, and OS3 specify whether
the drive is to be selected as drive I, 2, or 3, respectively.
For each drive, the strap for the desired drive number should
remain connected and the other two straps should be
disconnected. Straps can be disconnected by removing the
strap assembly from the DIP socket, spreading one of the pins
for each undesired strap and plugging the assembly back in
such that the spread pins are not inserted into the DIP
socket. Each drive should be programmed with a different
drive number. One drive must be number one.
To program a drive as drive number 4 perform the following
instructions on the printed circuit board mounted on top of
the disk drive.
a. Solder a jumper wire between pin 34 of edge connector Jl
and location IF pin 6. Take great care to connect the wire
to the very tip of pin 34 so that the ribbon cable
connector can slip as far onto Jl as possible.
b. Solder a jumper wire between IF pin 9 and IF pin 11.
c. The unmarked strap location between MX and MH at location
IF is now the location for programming drive 4. It can be
labeled OS4. This strap should remain connected and the
straps labeled OSl, OS2, and DS3 should be disconnected.
Be sure to disconnect this strap if the drive is ever
programmed to be drive 1, 2, or 3.
B. The strap labeled MX on the program shunt
should be disconnected. Be sure that the
(alternatively labeled HS on some drives)
and the MH strap remains disconnected.
(located at IF)
HL strap
remains connected
C. Five pull-up resistors for line termination on the ribbon
cable are located in the DIP resistor network at position lEo
Only the drive plugged in at the end of the ribbon cable
should have this resistor package plugged in. Additional
drives plugged in along the cable should have the resistor
package removed. In a dual-drive system, the resistor package
should be in the right-hand disk drive (drive #2).
North Star HORIZON Computer
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