Texas Instruments EUROTEXT CF70200 Manual page 9

UNIVERSAL TELETEXT DECODERS
'EUROTEXT' CF70200
2.4 TOP Mode
The TOP Mode can either be selected manually or may be selected automatically by EUROTEXT if
it is set to AUTO mode. In AUTO mode, the decoder will select TOP mode if it has received a valid
basic TOP table but has not received a valid packet 27 for the display page.
The EUROTEXT decoder has internal software to implement a TOP decoder without any external
microprocessor control. When TOP mode is selected the decoder will capture and store the basic
TOP table and up to three additional information tables. The TOP tables will be kept updated
automatically. Using the TOP tables, the decoder will automatically generate a row 24 display. The
user will be prompted with a warning message if an attempt is made to select a page which is not in
the transmission cycle, however, Eurotext will search for the selected page.
The coloured and index keys will have the following functions:
RED key This key will operate in one of two modes. It will either search backwards in the
TOP table and select the next page or the function of this key will depend upon the
display page. If a Block Page is displayed, it will select the last Block Page, if a
Group Page is displayed it will select the last Group or Block Page and if a Normal
Page is selected, it will select the last Block, Group or Normal Page.
GREEN key Next Block, Group or Normal Page
YELLOW key This key will operate in one of two modes. It will either search forwards in the TOP
table to find the next Block or Group Page, or it will find the next Group Page in the
current Block wrapping around in the block boundary.
CYAN key Next Block Page
INDEX key TV Block Page/P100. This key will select page 100 unless the display page is page
100 in which case it will select the first TV Block Page.
In all cases, the search for the block page will wrap-around from 899 to 100 and 100 to 899.
In TOP mode the EUROTEXT device uses an intelligent page capture strategy to select which pages
are to be stored in the four TOP stores. To give the user the fastest access to teletext pages, the pages
enabled for capture will depend upon the last page selected. The stores will always be programmed
with different page numbers.
DRAFT 11
'EUROTEXT'
15-Feb-96
CF70200
7
1Q96