MPI 40 Series - Functional Operations; Initialize; Drive Selection; Functional Operation

3.6 FUNCTIONAL OPERATIONS
3.6.1 Initialize
The Model 41/42 requires only two DC voltages for proper operation:
+ 24V + 2.4V DC and + SV + 0.25V DC. After power is applied, it is
necessary to wait about soo ms before the drive enters a ready
condition. The READY output (Pl-22) will go active after the SOOms
delay and the drive has been selected signifying that the read/write
operation may begin. This time is required to start the motor and
lock it to the specified rotational speed. The motor is started
whenever the MOTOR ON signal is sent to the spindle servo PCBA.
This is accomplished upon power up in the standard drive as jumper
B2-C2 places a ground on U2S-9 which causes MOTOR ON to go active.
With the spindle rotating and a diskette installed, the INDEX signal
(page 3, area D7) is monitored to determine when the diskette has
reached its nominal rotational speed. This is accomplished by the
retriggerable single-shot (U32-12) and the two D-type flip flops
(U33-ll, 3) which are clocked on each INDEX signal (area D6). If
the diskette is rotating at sub-nominal speed the single-shot (U32-
10) will toggle and keep the two flip flops in a reset condition.
Once nominal speed has been reached, the single-shot will cease
toggling and two INDEX signals will be counted, leaving both
flip flops set and the drive in a ready condition (U37-6 will be
high; area DS).
Prior to the first read/write operation, a "step out" operation must
be performed until the TRACK 00 interface line (Pl-42) becomes
active to initialize carriage position. Refer to figure 3-7.
When power is first applied the power up reset circuit, consisting
of UlO, R33, R34, and C25 (page 3, area C7), resets the stepper
phase selection flip flops, U7 (area C6), causing pins 6 and S to go
high. This will enable stepper motor phases one (J4-2) and four
(J4-1) (page 3, area B2) and partially enable the Track 00 gate, UlS
(area CS). If the carriage was positioned at track zero, JS-12
(area CS) would go high causing UlS-S to go high; sending the
TRACK 00 signal.
The MPI Model 40 Series provides a diskette in-place sensor, rather
than a Door Closed Switch. The drive can be ready and heads can be
loaded if the diskette is installed, the door is closed, and the
spindle is rotating at its nominal speed.
3.6.2 Drive Selection
There are four DRIVE SELECT interface lines (page 3, area AS) avail-
able to the controller. Also, there are four jumper lines available
on the drive. By jumpering these lines, one per drive, any one of
four drives can be selected by activating the corresponding DRIVE
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