Fujitsu M2361A Customer Engineering Manual page 136

(7) Offset
The head, being at the center of a track (On Track), is moved 100~ inches
in the direction specified by Bit 2 or 3 when TAG3 is sent from the
controller. The fine control method is used in this operation mode.
Figure 4.6.9 shows the timing diagram.
While the drive is selected (SLCT), Offset Plus (OFSTP) is set high when
Bit 2 of TAG3 is set to 1 by the controller and, at the same time, Offset
Out (OFSOT) is set high. If the drive is not in the abnormal condition
(ABN) at this time, Offset Active (OFACT) is set high and, at the same
time, Difference 16 (GDI6) is set high. Then, the servo control circuit
moves the head in the outer direction; i.e., the servo control circuit
starts the offset operation and moves the head to the location 100~ inches
outward of the on-track position. This operation is terminated within
5
ms.
When OFACT goes high, Offset Active Pulse (OFACP) is set high and the
5
IDs-timer is started (MSMS). At the same time, Seek End (SKEND) and
On
Cylinder (ONCYL) are set low. SKEND and ONCYL are set high when the timer
operation is terminated.
When Bit 3 of TAG3 is set to 1, Offset Minus (OFSTM) is set high and, by
holding OFSOT low, the head is moved in the inner direction.
When Bit 2 or Bit 3 of TAG3 is set to 0 and OFSTP, OFSTM, OFSTA, and GD16
are set low, the head is returned to the on-track position. This
operation is terminated within
5
ms.
When OFACT goes low, OFACP is set high, the
5
ms-timer (MSMS) is started
and, at the same time, SKEND and ONCYL are set low. When MSMS goes low,
SKEND is set high and, if th£ head is at the on-track position, ONCYL is
set high.
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