TPU2735 Ver la hoja de datos (PDF) - Unspecified

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TPU2735

Teletext Processor

Unspecified 

TPU 2735

7.4. The Display Selection Register, R-DS

R-DS controls the selection of a RAM sector for display.

The sector number of the displayed sector is either de-

termined by the TPU using R-PS or by the CCU.

R-DS Display Selection Register

address 0/24/20, 1-byte register

7.5. The Data Acquisition Control Register,

R-DAC

This register controls the slicer, the ghost compensation,

the acquisition of the page header and the skew data.

R-DAC Data Acquisition Control Register

address 0/24/21, 1-byte register

D7

TBD

D6

D5

DSEN RHA

D4

NRT

D3

NRH

D2

NDA

D1 D0

*

NGC RGC

D7 D6

D5 D4 D3 D2 D1 D0

*

*

*

*

*

*

ERS SIC NRS RPS RPSV MSB

LSB

Sector number of

displayed sector

ERS:

error flag of the selected page

ERS = 1 means: the selected page has been received

with errors. ERS is for internal use of the TPU 2735.

SIC:

start internal comparison

The CCU has to set SIC = 1 when a new page number

is loaded into R-PS. SIC is reset by the TPU when RPS

is valid.

NRS:

new request flag of the selected page

NRS = 1 means: the selected page has not yet been re-

ceived. NRS is only for internal use of the TPU.

RPS:

requested page is selected

The TPU sets RPS to 1 if a page number of one of the

eight request registers is identical to the selected page

number of R-PS (see section 9., “Two Ways to Select a

Page for Display”). When RPS is set to one and Display

(R-DC3) and Acquisition Block (R-MC) are different, the

current magazine (in parallel magazine mode) is taken

from R-PS.

RPSV:

RPS flag valid

Only if RPSV = 1 the value of RPS is valid. When R-PS

has been loaded with a new page number the TPU ac-

complishes a comparison within 20 ms. The result is

written into R-DS. When a comparison is accomplished

RPSV is set to 1. The CCU can reset RPSV after loading

R-PS and then check if RPSV is set to 1 again.

TBD:

vertical blanking delay

Set to 1 if the delay between horizontal and vertical

blanking pulse is more than 32 ms in field 1 of a TV

frame. TBD is used to adapt the TPU 2735 to different

sources of the blanking pulses required for synchroniza-

tion of the TPU (see Fig. 7–1). TBD must be set to 0 in

D2MAC mode.

DSEN:

deflection skew data enable

DSEN = 0: the horizontal display start is controlled by pin

11. DSEN = 1: the horizontal display start is controlled

by pin 31 (skew data).

The TPU 2735 is able to adjust the horizontal phase of

the Teletext RGB signal under control of deflection skew

data (DSD) at pin 31. The phase can be adjusted by

steps of 1/16 of the main clock period, i. e. 3.5 ns for PAL

and 4.4 ns for NTSC. DSD provides a Teletext picture

without visible jitter even when there is no color burst in

the video signal and the DPU is not in the locked mode.

For more details refer to the description of the DPU 25..

Deflection Processor.

RHA:

NRT:

NRH:

rolling header always

no rolling time

no rolling header

Refer to

Table

Rolling

Header

Options

NDA:

no data acquisition;

Default value is NDA = 0. If NDA = 1, the Teletext data

acquisition is switched off.

NGC:

no ghost compensation

NGC = 1 switches off the ghost compensation

RGC:

reset ghost compensation;

Zero written to this bit resets the ghost compensation fil-

ter; returns automatically to 1 when the reset command

is executed.

21

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