Page Capture Modes - Texas Instruments EUROTEXT CF70200 Manual

UNIVERSAL TELETEXT DECODERS
'EUROTEXT' CF70200
The EUROTEXT decoder can operate in four main modes of operation depending upon the
transmitted teletext signal and the controlling microprocessor. These modes are:
Normal
FLOF
TOP
Favourite Page
In EUROTEXT, the on-chip processor will automatically select the pages to be stored in memory in
all modes of operation except Favourite Page mode. EUROTEXT will implement an efficient page
capture algorithm which will ensure that only one version of any page is stored in the memory and
that all the pages will be kept updated with the latest data. When a page is received with the clear
page bit set, or the page is received for the first time, the decoder will clear the relevant page store
instantaneously. This allows the decoder to receive teletext signals using 'advanced page headers' or
'magazine shuffle'.
In addition to the four main modes of operation, the decoder has two additional modes of operation:
Menu Page
Sub Page.
In the Menu Page mode, the page stores 6 and 7 can be redefined as either two menu pages or as one
menu page and one page as a store for non-display packets. This mode allows the chip to be used for
PDC applications.
In the Sub Page mode, the decoder will capture the next two sub-pages of the display page.
In all modes, Teletext pages containing sub-titles can be directly selected.
The four modes of operation can be either selected directly or EUROTEXT can be set into an auto
mode. In auto mode, after a channel change command, the decoder will initially be in normal mode.
If a packet 27 designation code 0 for the display is received, the decoder will switch to FLOF mode.
If the decoder is in normal mode and receives a basic TOP table, it will switch to TOP mode.
In all modes of operation, the row 24 display can be either generated on-chip or can be written to by
the external microprocessor. The external microprocessor can also disable the display of row 24.
DRAFT 11

2.0 PAGE CAPTURE MODES

'EUROTEXT'
15-Feb-96
CF70200
3
1Q96