Correction In Trick Play Mode - Renesas Hitachi H8S/2194 Series Hardware Manual

28.6.6 f

Correction in Trick Play Mode

H
In trick play mode, the tape speed changes relative to the video head. This change alters the
horizontal sync signal (f
shifted to a different speed in each trick play mode, so as to obtain the normal horizontal sync
frequency. To shift the drum motor speed, software should modify the value written in the DFG
preset data register in the speed error detector.
This f correction can be expressed in terms of the basic frequency f
H
N
0
× f
f =
F
N +α (1−n)
0 H
Legend:
n: Speed multiplier (FWD = positive, REV = negative)
α
: H alignment (1.5H in standard mode, 0.75H in 2x mode, and 0.5H in 3x mode for
H
VHS and β systems; 1H for an 8-mm VCR)
N : Standard H numbers within field
0
f : Field frequency
F0
NTSC: N
0
PAL: N
0
), causing skew. To correct the skew, the drum motor speed must be
H
F0
= 262.5, f = 59.94
F0
= 312.5, f = 50.00
F0
of the drum as follows.
F
Rev. 2.0, 11/00, page 691 of 1037