TPU3035 Datasheet, PDF (48/73 Pages) Micronas – Teletext Processors

TPU 3035, TPU 3040
PRELIMINARY DATA SHEET
4.14. Subpage Manager
Any page in cycle can have a number of subpages, iden-
tified by subcode. In normal mode the subpage manager
will acquire only one subpage of every requested page.
This subpage can be any if subcode FFFF is requested
or it will be selected according to the requested subcode.
After a PAGE_REQUEST command with subcode F0xx,
the subpage manager will acquire all subpages of the
requested page. The subpages will be chained in the
same order as they are transmitted, i.e. every new sub-
code will be added at the end of chain. The page table
entry points to the subpage which was transmitted first
after the page request. The READ_PAGE_INFO com-
mand will reply the page table pointer and the actual
number of subpages in chain.
After a PAGE_REQUEST command with subcode F1xx,
the subpage manager will acquire all subpages of the re-
quested page but will allocate only a limited amount of
memory to store these subpages. The parameter “page
subcode low” will define the length (in number of sub-
pages) of a ring buffer in page memory which will hold
the recently received subpages. In this case, the
READ_PAGE_INFO command will return an index
pointing to the most recently updated subpage in chain,
together with the subcode of this page.
The DISPLAY_PAGE_REQUEST command searches
and displays a page according to the requested display
subcode. The search starts from page table and contin-
ues through the subpage chain if there is any. A rolling
header will be displayed if the requested subpage can-
not be found in memory.
A requested display subcode FFFF (don’t care subcode)
will only search and display the first subpage in chain,
thus there is no rolling subpage anymore. A DIS-
PLAY_PAGE_REQUEST command with subcode F0xx
(follow subcode) will search and display the last re-
ceived subpage in chain, thus it is possible to request all
subpages in background while still showing rolling sub-
pages in display.
Page Table
page pointer
subpage
pointer
page 100
subcode 0003
subpage
pointer
page 100
subcode 0001
0000
page 100
subcode 0002
Fig. 4–12: Subpage Organisation
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