Caption Data Transfer from the LC7455A/M to the Decoder IC (microcontroller): Method 1

(This is the basic technique.)

Notes: Applications that extract closed caption text data in mode 3 (NTSC TV) or mode 4 (PAL TV) must check the level of the O/E/CFOUT pin when an

LN21 falling edge is detected to determine whether odd field or even field data is being acquired.

(Caption data is transferred to the data output buffer.)

In modes 1 and 2, pulses are output on line 21 of even fields.

In mode 3, pulses are output on line 21 of both fields.

In mode 4, pulses are output on line 22 of both fields.

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(The decoder IC (microprocessor) sets CE from high to low after detecting a falling edge on LN21.)

High impedance

The previous data is output.

(Sixteen bits of caption data is output LSB first in synchronization with falling edges on SCKIN.)