28.15.6 Noise Detection - Renesas Hitachi H8S/2194 Series Hardware Manual

28.15.6 Noise Detection

If drop-out of a pulse of the horizontal sync signal occurred, set a supplemented pulse at the
timing set in HPWR and with the set pulse width.
Set the noise detection window with HWR of about 1/4 of the horizontal sync signal, and the
pulse with equal High and Low periods will be obtained.
(1) Example of Setting
Assumed that a supplemented pulse is set when fosc = 10MHz under the conditions φs =
5MHz, NTSC:TH = 63.6 (µs) and Hpuls = 4.7 (µs), the set values of the supplemented pulse
timing (HRTR7-0), supplemented pulse width (HPWR3-0) and noise detection window
timing (NWR5-0) are expressed by the following equations.
(Value of HRTR7-0) × 2/φs = TH
((Value of HPWR3-0) + 1) × 2/φs = Hpuls
((Value of NWR5-0) + 1) × 2/φs = 1/4 × TH
Where, TH is the cycle of the horizontal sync signal (µs), Hpuls is the pulse width of the
horizontal sync signal (µs) and φs is the servo clock (Hz) (fosc/2).
Accordingly,
(Value of HRTR7 to HRTR0) × 0.4 (µs) = 63.6 (µs)
∴HRTR7-0=H'9F
((Value of HPWR3 to HPWR0) + 1) × 0.4 (µs) = 4.7 (µs)
∴HRTR3-0=H'B
((Value of NWR5 to NWR0) + 1) × 0.4 (µs) = 16 (µs)
∴NWR5-0=H'27
Also, the noise mask period is computed as follows.
((Value of HRTR7 to HRTR0) + 1) − 24) × 2/φs = 54 (µs)
Where, 24 is a constant required for a structural reason.
Figure 28.75 shows the set period for HRTR, HPWR and NWR.
Rev. 2.0, 11/00, page 806 of 1037