Section 28 Servo Circuits; Overview; Functions - Renesas Hitachi H8S/2194 Series Hardware Manual

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
(1) Input and output
circuits
(2) Error detectors
(3) Phase and gain
compensation
(4) Other circuits

Section 28 Servo Circuits

Function
CTL I/O amplifier
CFGDuty compensation
input
DFG, DPG
separation/overlap input
Reference signal
generators
HSW timing generator
Four-head high-speed
switching circuit for
special playback
12-bit PWM
Frequency division
circuit
Sync detection circuit
Drum speed error
detector
Drum phase error
detector
Capstan speed error
detector
Capstan phase error
detector
X-value adjustment and
tracking adjustment
circuit
Digital filter computation
circuit
Additional V signal
circuit
CTL circuit
Description
Gain variable input amplifier
Output amplifier with rewrite mode
Duty accuracy: 50±2%
(Zero cross type comparator)
Overlap input available: Three-level input
method, DFG noise mask function
V compensation, field detection, external signal
sync, V sync when in REC mode, REF30 signal
output to outside
Head-switching signals, FIFO 20 stages
Compatible with DFG counter soft-reset
Chroma-rotary/head-amplifier switching output
Improved speed of carrier frequency
With CFG mask, no CFG for phase or CTL
mask
Noise count, field discrimination, Hsync
compensation, Hsync detection noise mask
Lock detector function, pause at the counter
overflow, R/W error latch register, limiter function
Latch signal selectable, R/W error latch register
Lock detector function, pause at the counter
overflow, R/W error latch register, limiter function
R/W error latch register
(Separate setting available)
Computations performed automatically by
hardware
Output gain variable: × 2 to × 64 (exponents of 2)
-1
(Partial write in Z (high-order 8 bits) available)
Valid when in special playback
Duty discrimination circuit, CTL head R/W
control, compatible with wide aspect
Rev. 2.0, 11/00, page 611 of 1037