MPI 40 Series - Step; Write Gate; Write Data; Head Load (Alternate Input)

3.5.1.5 Step
This input line is normally in the inactive state (logical
one). Each pulse causes the read/write heads to move one track
"in" or "out" from the present position, depending upon the
status of the DIRECTION SELECT line as explained in paragraph
3.5.1.4. The access motion is initiated on the trailing edge or
low to high transition. Any change in the DIRECTION SELECT line
must be made at least 200ns before the trailing edge of the STEP
pulse. Figure 3-7 shows the timing for STEP pulses.
3.5.1.6 Write Gate
The active state (logical zero) of this line enables data to
be written on the diskette. The inactive state (logical one)
allows for a "read" operation and enables the stepper logic.
Figure 3-8 shows the timing constraints for a "write" operation.
3.5.1.7 Write Data
This input, together with WRITE GATE (active low), provides the
data to be written on the diskette of the selected drive.
The data should be encoded (FM or MFM) prior to sending it to
the drive. Each transition from high to low on this line
will reverse the write current in the read/write head thereby
writing a data bit. In the selected drive, the WRITE GATE line
enables this input line. See Figure 3-8 for timing.
3.5.1.8 Head Load (Alternate Input)
This input line is a user installable option which is enabled by
jumpering C3 - C4 in the drive. When this option is used and
activated (logical zero) and the drive is ready, the read/write
heads will be loaded against the diskette. Refer to paragraphs
6.3 and 6.4 for installation and a detailed description.
3.5.1.9 In Use (Alternate Input)
This input line has been designated a spare I/O pin.
3.5.1.10 Write Current Switch (Alternate Input)
This input line is a user installable option enabled by jumpering
J12 - K12 in the drive. This input line is an alternate function
with the Track 43 Internal Sensor signal in the drive. When
active (logical zero), this input line lowers the write current
for tracks 43 thru 77. Inner tracks have more flux reversals per
inch than that of outer tracks which requires lowering the write
current for the inner tracks. Refer to paragraph 6.8.
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