ADV7344 datasheet(49/88 Pages) AD

49 / 88 page

ADV7344

Rev. 0 | Page 49 of 88

ED/HD TIMING RESET

Subaddress 0x34, Bit 0

An ED/HD timing reset is achieved by toggling the ED/HD

timing reset control bit (Subaddress 0x34, Bit 0) from 0 to 1. In

this state, the horizontal and vertical counters remain reset. When

this bit is set back to 0, the internal counters resume counting.

This timing reset applies to the ED/HD timing counters only.

SD SUBCARRIER FREQUENCY LOCK, SUBCARRIER

PHASE RESET, AND TIMING RESET

Subaddress 0x84, Bits[2:1]

Together with the SFL/MISO pin and SD Mode Register 4

(Subaddress 0x84, Bits[2:1]), the ADV7344 can be used in

timing reset mode, subcarrier phase reset mode, or SFL mode.

Timing Reset (TR) Mode

In this mode (Subaddress 0x84, Bits[2:1] = 10), a timing reset is

achieved in a low-to-high transition on the SFL/MISO pin (Pin 48).

In this state, the horizontal and vertical counters remain reset.

Upon releasing this pin (set to low), the internal counters

resume counting, starting with Field 1, and the subcarrier phase

is reset. The minimum time the pin must be held high is one

clock cycle; otherwise, this reset signal might not be recognized.

This timing reset applies to the SD timing counters only.

Subcarrier Phase Reset (SCR) Mode

In this mode (Subaddress 0x84, Bits[2:1] = 01), a low-to-high

transition on the SFL/MISO pin (Pin 48) resets the subcarrier

phase to 0 on the field following the subcarrier phase reset. This

reset signal must be held high for a minimum of one clock cycle.

Because the field counter is not reset, it is recommended that

the reset signal be applied in Field 7 (PAL) or Field 3 (NTSC).

The reset of the phase then occurs on the next field, that is,

Field 1, lined up correctly with the internal counters. The field

count register at Subaddress 0xBB can be used to identify the

number of the active field.

Subcarrier Frequency Lock (SFL) Mode

In this mode (Subaddress 0x84, Bits[2:1] = 11), the ADV7344

can be used to lock to an external video source. The SFL mode

allows the ADV7344 to automatically alter the subcarrier

frequency to compensate for line length variations.

When the part is connected to a device such as an ADV7403

video decoder (see Figure 62) that outputs a digital data stream

in the SFL format, the part automatically changes to the

compensated subcarrier frequency on a line-by-line basis. This

digital data stream is 67 bits wide, and the subcarrier is

contained in Bit 0 to Bit 21. Each bit is two clock cycles long.

DISPLAY

NO TIMING RESET APPLIED

TIMING RESET APPLIED

START OF FIELD 4 OR 8

FSC PHASE = FIELD 4 OR 8

FSC PHASE = FIELD 1

TIMING RESET PULSE

307

310

307

12345

313

320

DISPLAY

START OF FIELD 1

Figure 60. SD Timing Reset Timing Diagram (Subaddress 0x84, Bits[2:1] = 10)

NO FSC RESET APPLIED

FSC PHASE = FIELD 4 OR 8

307

310

313

320

DISPLAY

START OF FIELD 4 OR 8

FSC RESET APPLIED

FSC RESET PULSE

FSC PHASE = FIELD 1

307

310

313

320

DISPLAY

START OF FIELD 4 OR 8

Figure 61. SD Subcarrier Phase Reset Timing Diagram (Subaddress 0x84, Bits[2:1] = 01)

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