Fujitsu M2361A Customer Engineering Manual page 133

(6) Seek
The head is moved to the cylinder specified by Tag l/Bits 0 - 9 sent from
the controller. Figure 4.6.8 shows the timing diagram.
a. State 05 (Accelerate)
When TAGI goes high, the contents of Bits
0
to
9
are set in the New
Cylinder Address Register (NCAR). The address of the cylinder on
which the head is currently located is stored in the Present Cylinder
Address Register (PCAR). The difference between the address stored
in the NCAR and that in the PCAR is calculated and is output in the
binary code (Dl - D128). If the difference is 144 or greater (NCAR -
PCAR> 144), Dl - D128 is set to a value of alII bits and is sent to
the servo control circuit. The servo control circuit forms the
desired speed curve according to the value indicated by Dl - Dl28.
If the value indicated by the NCAR is greater than that indicated by
the PCAR, Move Out Gate (MVOTG) is set high to cause the head to be
moved in the outer direction; conversely, if the value indicated by
the NCAR is smaller than that indicated by the PCAR, NVOTG is set low
to cause the head to be moved in the inner direction.
Then, when TAGl goes low, Set CAR Off Pulse' (SCAROFP) is set high,
SKEND, ONCYL, TFTMR, and LNML are set low, and Access Mode (ACCMD) is
set high.
The servo control circuit moves the head according to the desired
speed curve and generates Track Crossing Pulse (TRXGP) whenever the
head crosses a cylinder. TRXGP is sent to the PCAR to increment the
register when the head is moved in the outer direction, or to
decrement the register when the head is moved in the inner direction.
Thus, the output of the difference counter (Dl - Dl28) is decremented
by one at a time.
b. StateOl (Decelerate)
If the head is moved at
a
speed higher than that indicated by the
desired speed curve, the servo control circuit generates End
Accelerate (ENDAC) and sets CNTL low. The speed of the head is then
reduced so that the head is moved according to the desired speed
curve.
c. Sta te 03 (Seek Linear Mode)
4 - 62
When the head detects On Cylinder at the desired cylinder
(NCAR=PCAR), the servo control circuit generates End Decelerate
(ENDDC) and, at the same time, starts the 2.5 ms-timer and sets LNML
high. Then, the operation mode of the head is changed from the
position curve control mode to the position error control mode.
B03P-4825-0002A ... 01A