ST92196A datasheet(166/268 Pages) STMICROELECTRONICS

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- CLOSED CAPTION DATA SLICER (DS)

DATA SLICER (Cont’d)

Bit 4 = SEARCH: Enhanced Signal Search.

This bit is set and cleared by software. This bit

should be set to improve the reliability of properly

identifying signals in closed caption and Gemstar

format when doing a search encompassing all hor-

izontal lines in the vertical blanking interval.

0: Check 5 bits in the Frame code

1: Check 8 bits in the Frame code

Bit 3 = SCG_EN:

Block Copy-Guard signals.

In video signals with Copy-Guard protection puls-

es similar to horizontal sync pulses may have

been inserted into certain lines in the vertical

blanking interval.

0: No blocking

1: Copy-Guard pulse occurring 8 µs before the an-

ticipated occurrence of normal horizontal sync

pulses are blocked from reaching the line detec-

tion logic

Bit 2 = PHD[2:0]:

Horizontal phase compensation.

These bits specify the delay added in 4µs incre-

ments to the clock for the half-line counter in logic

that identifies the specified line. This feature is

used in 2H mode of operation to compensate for a

large phase difference which may exist between

2H deflection pulses and horizontal sync pulses

extracted from video.

MONITOR REGISTER (MR)

R246 - Read/Write

Reset Value: 0000 0000 (00h)

Bit 7 = CCMODE:

Closed Caption Mode.

This bit is set by hardware and cleared by soft-

ware.

0: No closed caption format detected

1: Closed caption format detected

Bit 6 = GSMODE:

Gemstar Mode.

This bit is set by hardware and cleared by soft-

ware.

0: No Gemstar format detected

1: Gemstar format detected

Bit 5= FIELD1:

Field 1 flag.

This bit is set and cleared by hardware.

0: Field 2 detected

1: Field 1 detected

WARNING: The bit value is not valid after tuning of

a new channel or in case of a momentary drop-out

of the tuned signal. In this case, the use of the

IN_SYNC bit is required.

Bit 4= IN_SYNC:

Phase of line monitoring relative

to video field.

This bit is set and cleared by hardware. Software

should read this bit periodically in case data in

closed caption and/or Gemstar format must be re-

covered from lines in both fields (e.g. closed cap-

tions from Line#21 of Field1 and extended data

service information from Line#21 of Field2).

0: Periodic writing of the appropriate line codes

into Register CR1 is out of phase with the field

sequence of the video input signal. In this case

the phasing can be corrected by skipping just

once the change of the line code stored in the

CR1 register and writing the immediately follow-

ing field.

1: The start of a specified line has been detected in

one or both of the last 2 fields.

Note: In situations where the closed caption or

Gemstar data is on lines which are all in the same

field, e.g. Field#1, the hardware in the data slicer

cell will automatically correct an out-of-phase situ-

ation. Such a situation will be corrected within the

period of one frame of video.

In a more general situation, data must be recov-

ered from lines in both fields, and then the hard-

ware cannot on its own correct the polarity of an

out-of-phase FIELD#1 signal. The correction must

therefore be done by software on basis of informa-

tion provided by the IN_SYNC status bit.

Bit 3:0= EVNP[4:1]:

Parity Event Bits

These bits are set and cleared by hardware. They

indicate the detected parity of data bytes 1 through

4 (only 3 and 4 for closed caption format). These

bits should normally be low.

0: Odd parity detected

1: Even parity detected

MODE

FIELD

IN_SY

EVNP

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