Lucent Technologies MN10285K - Manual (Page 203)

On-Screen Display
Field Detection Circuit
Panasonic Semiconductor Development Company MN102H75K/F75K/85K/F85K LSI User Manual
202
Panasonic
7.14.3 Considerations for Interlaced Displays
■ Switching the display start field
The OSD is constructed so the display start position is the field (field 1) where
the EOMON bit is 1. However, interlaced displays may require that the start
position be a field (field 2) where the EOMON bit is 0. In this case, merely com-
plementing the EOSEL bit will not result in a correct display. You must set the
following two bits to have the display start at field 2.
♦ CANH (x’007F0A’, bit 4): Set to 1.
0: Normal display
1: Slide the field 1 display position down 1 line
♦ EOSEL (x’007F0E’, bit 10): Complement the value EOSEL has for
field 1 in a normal display.
■ Scrolling in the closed-caption mode
To implement text-layer scrolling in the closed-caption mode, the program must
constantly switch the text display fields. This can cause the text lines to display
incorrectly. To prevent this, set the following bits to fix the text lines to the even
or odd field characters while scrolling.
♦ BFLD (x’007F0A’, bit 2): Set to 1 to enable scrolling.
0: Normal display
1: Display the same characters in fields 1 and 2
♦ EONL (x’007F0A’, bit 3): Set to 0 or 1.
0: Fix to characters in field 1
1: Fix to characters in field 2
Table 7-15 EOMON Output Criteria
FRMON N1, N2 Relationship
EOMON Output
EOSEL = 0 EOSEL = 1
0
Load to N2 next
N1 > N2 0 1
N1 < N2 1 0
N1 = N2 Complement previous Complement previous
1
Load to N1 next
N1 > N2 1 0
N1 < N2 0 1
N1 = N2 Complement previous Complement previous