System Block Diagram

No. 5680-3/13

LC7455A, 7455M

Operation in the Different Modes

Pin

Application

Mode

equipment

Operation

MOD1

MOD0

· Even field line 21 data extraction

Open

Open

Mode 1

VCR

The internal PLL is operated with the horizontal synchronizing signal separated from the composite video

signal as the reference.

· Even field line 21 data extraction

Open

Mode 2

VCR

An external 508 kHz ceramic oscillator is used, and the internal PLL is operated with that oscillator output

divided by 32 as the reference.

Open

Mode 3

NTSC-TV

· Odd and even field line 21 data extraction

The internal PLL is operated with the Hsync signal applied from fly back as the reference.

Mode 4

PAL-TV

· Odd and even field line 22 data extraction

The internal PLL is operated with the Hsync signal applied from the fly back circuit as the reference.

Note: The data extraction operations in modes 1 and 2 are identical. However, while mode 1 can operate without problem for normal "on air" signals, it may

be difficult for the PLL to lock with signals such as scrambled CATV signals.

PLL reference clock

mode 2

mode 3, 4

mode 1

Data peak hold

(Data slice)

Hsync peak hold

(Hsync slice)

Output control

Data output

buffer

Divided-by-

32 circuit

Oscillator

circuit

Pedestal clamp

(Mode 2)

(Mode 2)

(Modes 1, 3, 4)