ST72774 datasheet(64/144 Pages) STMICROELECTRONICS

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ST72774/ST727754/ST72734

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SYNC PROCESSOR (SYNC) (Cont’d)

4.4.7 Output Processing

4.4.7.1 Generating Free-Running Frequencies

The free-running frequencies function is used to:

– Drive the monitor when no or bad sync signals

are received.

– Stabilize the OSD screen when the monitor is

unlocked.

– Perform fast alignment for maintenance purpos-

es.

Note: When free-running mode is active, the analyzer

and corrector modes must be disabled.

– VCORDIS = 1, VEXT = 0 in CFGR and POLR

registers for vertical output measurement

– 2FHINH = 0 in CFGR register for horizontal

low level measurment

– VACQ, HACQ = 0, in CFGR register for ana-

lyzer mode

The Sync processor can generate any of the

following output sync signals HSYNCO, VSYNCO,

CLAMPOUT, BLANKOUT.

To select the generation mode:

– Program the horizontal period using the HGENR

– Program the vertical period using the VGENR (8

bits) and CFGR (3 bits) registers (2047 scan

lines per frame). Refer to Figure 44.

– Configure the following bits:

SYNOP = 0

HVGEN = 1

HACQ = 0

VACQ = 0

Horizontal Period

PH = Horizontal period = ((HGENR+1)/4) µs

Pulse width: 2 µs => HGENR min=8

Polarity: Positive

HGENR range: [8..255]

Vertical Period

PV = Vertical period = (PH * V11bits) µs

V11bits is a concatenation of VGENR and the Q'2

Q'1 Q'0 bits of the CFGR register.

Refer to Figure 44.

Pulse width: 4 * PH => min value= 8µs

Polarity: Positive

VGENR/CFGR range: [5..7FF]

Table 17. Typical values for generated HSYNC signals

Table 18. Typical values for generated VSYNC signals

HGENR (hex value)

H Period

HFREQ

Pulse Width

Duty Cycle

5 µs

200 kHz

2 µs

40%

8 µs

125 kHz

2 µs

25%

16 µs

62.5 kHz

2 µs

12.5%

32 µs

31.25 kHz

2 µs

6.2%

64 µs

15.6 kHz

2 µs

3.1%

HGENR

(hex value)

H Period

H Freq

V11bits

(hex value)

V Period

V Freq

Pulse width

5 µs

200 kHz

7FF (2047)

10.2 ms

97.7 Hz

20 µs

5 µs

200 kHz

400 (1024)

5.1 ms

195 Hz

20 µs

8 µs

125 kHz

7FF (2047)

16.3 ms

61 Hz

32 µs

8 µs

125 kHz

400 (1024)

8.2 ms

122 Hz

32 µs

16 µs

62.5 kHz

7FF (2047)

32.6 ms

30.6 Hz

64 µs

16 µs

62.5 kHz

400 (1024)

16.4 ms

60.9 Hz

64 µs

32 µs

31.25 kHz

7FF (2047)

65.5 ms

15 Hz

128 µs

32 µs

31.25 kHz

400 (1024)

32.8 ms

30 Hz

128 µs

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