Fujitsu M2361A Customer Engineering Manual page 156

o. Velocity level detector
The velocity level detect circuit slices the velocity signal (VLTY)
and sends CAPVL and *VG20I signals to the logic circuit. CAPVL,
which indicates the carriage Velocity is lower than the specified
value, is used to prevent the rezero operation from being started
while the carriage is being moved at high speed, and also used to
provide switching moment from coarse control to fine control.
*VG20I, which indicates the carriage velocity is too high during the
rezero operation, is used to monitor the access mechanism.
p. Velocity error circuit
The velocity error circuit generates the velocity error signal
(VLERR) which indicates a difference between the target velocity
signal VLGDA and the actual velocity signal VLTY. It also generates,
by slicing VLERR, the end accelerate signal (ENDAC) which indicates
the end of acceleration.
q. End decelerate detector
The end decelerate detect circuit generates the End Decelerate signal
(*ENDDC) which indicates switching of the control mode from the
coarse control to the fine control. That is, the circuit generates
*ENDDC after the specified time has elapsed from the moment *ONTRK
goes low and *EQUAL is low. At this time, CAPVL is used to indicate
that the velocity is lower than the specified velocity.
r. Timer
The timer is used to generate the Track Following Timer signal
(TFTMR) which informs the logic circuit that the access operation has
been completed normally after the specified time period from the
moment the control mode had been switched to the fine control or, it
sends the Access Timeout signal (ACTMO), which indicates that the
operation has not been completed within the specified time period
after the start of movement. It also provides the time setting
signal (M3M, *OFINT) to be used during an offset operation.
s. Reference voltage generator
The reference voltage generator generates -4V and +6V reference DC
voltages to be supplied to the head IC on the servo head assembly.
They are also used as reference voltages for various level detect
circuits and the desired velocity level during a rezero operation.
t. Servo logic
The servo logic generates various signals used in coarse control and
fine control based on the control logic signals sent from the logic
circuit.
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