- 51 -
can always be overridden by the user after the event.
Each line on the diagram, with its associated text, represents the exact conditions under which the change of state will
occur. Sometimes this will be accompanied by another action which will be automatically performed by the television,
being to either ENABLE or DISABLE F/SW 1.
5-4-7 Over Current Protection
In case of overload, the SMPS secondary voltages will drop. The voltage on pin 64 of microcontroller drops below a
reference voltage (2.26V). The controlling software which continuously monitors this voltage will switch the set to
stand by mode. To power on the set again the user must switch it off using the main power switch. Appropriate hyster-
esis guaranrees a reliable operation.
5-5 Teletext Display
National character option bits C12, C13, C14 are transmitted in the page header of a given teletext page. The national
option bits are intended to change (or exchange) 13 characters within the G0 character set, according to the needs of
each national language. However, for Cyrillic and Greek languages, a major character set change (a change of character
mapping) needs to effected for correct display.
These codes represent, for a given broadcaster, the intended language that the teletext page should be displayed in. As
there are only 3 bits, there are only 8 codes available to cover all the possible language combinations. This means that
for a received code there are several possibilities meanings, and therefore several possibilities for display.
This is not as bad as it first seems, as we use the user-selected OSD language to identify the intention of the broadcaster.
For example, a user wishing to see Russian teletext should select Russian OSD language, otherwise he would not have
correct teletext display on the TV.
The table below allows the reader to understand the relationship between selected OSD language (which is under user
control), the teletext language display (selected by national option bits in transmission page header) and the language
mapping (either Latin or Greek/Cyrillic)
An example: For Greek teletext display, (if national option code 1 1 1 is received from the broadcaster), the user should
select the Greek OSD language. Even if English, French, German, Italian, Spanish, Dutch, Danish, Finnish, Norwegian
or Swedish OSD languages are selected, the teletext will be correctly displayed.
However, if Polish, Hungarian, Czech, Slovakian, Rumanian or Russian OSD are selected, Latin font mapping is
selected. The consequence will be incorrect teletext display, with NO GREEK CHARACTERS DISPLAYED. Roma-
nian national font options will be selected.
Summary of Contents for DTP-28B1
Page 29: ...29 Block diagram TDA8944J...
Page 32: ...32...
Page 34: ...34 Block diagram TDA6107Q...
Page 39: ...39 5 Circuit description 5 1 Block diagram...
Page 57: ...57 5 9 2 2 STR F6654 oscillating operation...
Page 73: ...73 7 Exploded View 7 5 DTP 28B1...
Page 74: ...PRINTED CIRCUIT BOARD PCB MAIN...
Page 75: ......
Page 76: ......
