GENNUM CORPORATION

522 - 47 - 00

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4. FLY WHEEL OPERATION

The flywheel logic will check the incoming video data for

valid video lines. If the incoming data represents a valid

line, the flywheel remains in sync with the incoming data. If

the incoming data represents an invalid line, the flywheel

will use the stored timing information for the past valid line

to generate the output HVF timing signals until three (3)

consecutive lines having identical timing are detected. In

this case, the new timing information will be saved and the

flywheel

operation

is

updated

to

this

new

timing.

Mismatches between the HVF information decoded from

the data stream and that indicated by the flywheel will

trigger the EAV_ERR and SAV_ERR signals as shown in

Figure 3. HVF output timing is shown in Figure 2.

5. AUTOMATIC SWITCH LINE LOCK HANDLING

The automatic switch line lock is based on the assumption

that the switching of video sources will only cause the H

signal to be out of alignment whereas V and F signals

remain in sync; i.e. switching between video sources of the

same format. Therefore, when in the automatic switch line

lock mode (FAST_LOCK transitions for low to high), the

flywheel positive H signal transition will align with the

detected positive H signal transition. Timing for the

FAST_LOCK signal is shown in Figure 5.

TABLE 1: Source Format Parameters

Reference SMPTE

Standard

260m

260m

295m

274m

274m

274m

274m

274m

274m

274m

274m

296m

296m

Format ID

A

B

C

D

E

F

G

H

I

J

K

L

M

Lines/Frame

1125

1125

1250

1125

1125

1125

1125

1125

1125

1125

1125

750

750

Words/Active Line

(each channel Y,

Cb/Cr)

1920

1920

1920

1920

1920

1920

1920

1920

1920

1920

1920

1280

1280

Total Active Lines

1035

1035

1080

1080

1080

1080

1080

1080

1080

1080

1080

720

720

Words/Total Line

(each channel Y,

Cb/Cr)

2200

2200

2376

2200

2200

2640

2200

2200

2640

2750

2750

1650

1650

Frame Rate (Hz)

30

30/M

25

30

30/M

25

30

30/M

25

24

24/M

60

60/M

Fields /Frame

222

222

1111

111

Data Rate Divisor

1

M

1

1

M

1

1

M

1

1

M

1

M

NOTE: M=1.001 in the above table.