Rev. 1.0, 02/00, page 614 of 1141
26.5
High-Speed Switching Circuit for Four-Head Special Playback
26.5.1
Overview
This high-speed switching circuit generates a color rotary signal (C.Rotary) and head-amplifier
switching signal (H.Amp SW) for use in four-head special playback.
A pre-amplifier output comparison result signal is input from the COMP pin. The signal output to
the C.Rotary pin is a chroma signal processing control signal. The signal output at the H.Amp SW
pin is a pre-amplifier output select signal. To reduce the width of noise bars, the C.Rotary and
H.Amp SW signals are synchronized to the horizontal sync signal (OSCH). OSCH is made by
adding supplemented H, which has been separated from Csync signal in the sync signal detector
circuit. For more details of OSCH, see section 26.15, Sync Signal Detector.
If the VCR system does not require this circuit, C.Rotary, H.Amp SW, and COMP pins can be
used as the I/O port.
26.5.2
Block Diagram
Figure 26.26 shows the block diagram of this circuit.
W
W
Synchronization
control
CHCR
W
CHCR
RTP0
H.Amp SW
C.Rotary
OSCH
(Synchronization)
COMP
NarrowFF
VideoFF
W
CHCR
Internal bus
Internal bus
HAH
CRH
W
CHCR
SIG3 to 0
HSWPOL
V/N
Decoding circuit
Figure 26.26 High-Speed Switching Circuit for Four-Head Special Playback