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Rev. 2.0, 11/00, page 611 of 1037
Section 28 Servo Circuits
28.1
Overview
28.1.1
Functions
Servo circuits for a video cassette recorder are included on-chip.
The functions of the servo circuits can be divided into four groups, as listed in table 28.1.
Table 28.1 Servo Circuit Functions
Group
Function
Description
CTL I/O amplifier
Gain variable input amplifier
Output amplifier with rewrite mode
CFGDuty compensation
input
Duty accuracy: 50
±
2%
(Zero cross type comparator)
DFG, DPG
separation/overlap input
Overlap input available: Three-level input
method, DFG noise mask function
Reference signal
generators
V compensation, field detection, external signal
sync, V sync when in REC mode, REF30 signal
output to outside
HSW timing generator
Head-switching signals, FIFO 20 stages
Compatible with DFG counter soft-reset
Four-head high-speed
switching circuit for
special playback
Chroma-rotary/head-amplifier switching output
12-bit PWM
Improved speed of carrier frequency
Frequency division
circuit
With CFG mask, no CFG for phase or CTL
mask
(1) Input and output
circuits
Sync detection circuit
Noise count, field discrimination, Hsync
compensation, Hsync detection noise mask
Drum speed error
detector
Lock detector function, pause at the counter
overflow, R/W error latch register, limiter function
Drum phase error
detector
Latch signal selectable, R/W error latch register
Capstan speed error
detector
Lock detector function, pause at the counter
overflow, R/W error latch register, limiter function
Capstan phase error
detector
R/W error latch register
(2) Error detectors
X-value adjustment and
tracking adjustment
circuit
(Separate setting available)
(3) Phase and gain
compensation
Digital filter computation
circuit
Computations performed automatically by
hardware
Output gain variable:
×
2 to
×
64 (exponents of 2)
(Partial write in Z
-1
(high-order 8 bits) available)
Additional V signal
circuit
Valid when in special playback
(4) Other circuits
CTL circuit
Duty discrimination circuit, CTL head R/W
control, compatible with wide aspect
Содержание Hitachi H8S/2191
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Страница 639: ...Rev 2 0 11 00 page 612 of 1037 28 1 2 Block Diagram Figure 28 1 shows a block diagram of the servo circuits...
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