Tandon TM100-1 Operating And Service Manual page 40

6 . Input diodes to the read amplifier are
reverse biased by N Write to protect the
read am plifier during the write
operation.
7 . The write data input is inverted and used
to clock the waveform generator which
selects a write driver, thus providing a
ground to forward bias a diode, allowing
current to flow through the coil.
When there is a pre-erase delay 390-microsecond
time out, the erase current source is turned on.
The clocking of the waveform generator during
write operation provides a trigger to the post­
erase delay one shot, and does not allow it to
time out until all data is written.
N Internal Write Busy is active until the end of
the post-erase delay, and keeps +12 volts D. C.
on the read/write diode matrix during the erase
time.
The duration of a write operation is from the
true going edge of Write Enable to the false
going edge of Trim Erase. This is indicated by
the Internal Write Busy waveform (Figure 4-8).
READ DATA CIRCUITS
The read electronics consist o f:
1 . Read Only and Side Select circuits
2 . Read Amplifier and Linear Phase Filter
3 . Differentiator
4 . Comparator, Time Domain Filter, and
Digitizer
The Read Only circuits are used to isolate the
read amplifier from the voltage excursion across
the head during a write operation. The side
select is used to enable one of the read/write
head(s).
The drive must be in a ready condition before
reading can begin. This ready condition must he
established by the user system. In addition to
the requirements established in this section, a
100 microsecond delay must exist from the trail­
ing edge of the Trim Erase signal to allow the
read amplifier to settle after the transient
caused by the Read Only circuit returning to the
Read mode.
The output signal from the read/write head is
amplified by a read amplifier, and filtered by a
linear phase filter to remove noise. The linear
output from the filter is passed to the differen­
tiator, whicli generates a waveform whose zero
crossovers correspond to the peaks of the Read
signal, then, this signal is fed to the comparator,
time domain filter, and digitizer circuitry
(Figure 4-9).
4.6 SPINDLE CONTROL
The components of the drive required to control
the spindle are:
1 . Spindle Motor and Spindle Assembly
2 . Spindle Motor Enable circuit
3 . Spindle Motor Control circuit
SPINDLE MOTOR AND SPINDLE
ASSEMBLY
The Spindle Assembly is driven by a belt at­
tached between two pulleys. The drive motor
pulley is turned by a D. C. motor with a built in
integral tachometer. The spindle pulley connects
to a hub that rotates a clamped diskette.
SPINDLE MOTOR ENABLE CIRCUIT
The Motor On signal is derived from the host
controller to the interface connector via Jl, Pin
16. This signal is buffered and supplied to the
servo circuit board, which uses it to enable the
motor current circuit of the spindle motor
control.
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