
Philips Semiconductors
Video Out
File: evo.fm5, modified 7/24/99
PRELIMINARY INFORMATION
7-23
7.21
EVO DATA-STREAMING MODE
When EVO_ENABLE and SYNC_STREAMING flags
are set, the pin VO_IO2 indicates a data valid signal.
This signal is set when EVO start outputting valid data
(i.e. data streaming mode enable and video out running),
and is reset when the data streaming mode is cancelled
The data valid signal on VO_IO2 is set just before that
the first valid byte is present on VO_DATA[7:0], and re-
set just after the last valid byte was sent, or if HBE error
is signaled. All signal start change on rising VO_CLK
edge. VO_IO1 generates a one VO_CLK pulse one
VO_CLK cycle before the first valid data.
7.22
FRAME SYNCHRONIZATION
When
EVO_ENABLE
and
FIELD_SYNC
are
set,
VO_IO2 will indicate the field number (low= field 1, high
= field 2), according to the SAV/EAV field indication
(bit[6]). The pin VO_IO2 toggles just before the first byte
of the preamble that protects the EAV code, and after the
SAV code. Non-interlaced output is simulated by pro-
gramming Video Out to generate fields equivalent to the
desired frames. In this case, VO_IO2 indicates odd or
even frames.
7.23
ALPHA BLENDING
The alpha blending uses a 8-bit word alpha as value for
merging the overlay plane with the image plane. The
MSB is used to switch on the blending (MSB = 0) or to
select the overlay plane as only output (MSB = 1). There-
fore, we have 128 + 1 (00h to 0x7F for blending values,
and 0x80 to 0xFF for 100% overlay). A 00h alpha value
leads to 100% image plane and 0% overlay. Similarly, a
40h value lead to 50% image and 50% overlay. EVO
supports the 129 levels that can be encoded in 8 bits
(Video Out only supports 5 levels for blending). The
equation for the blending is:
VO_DATA[7:0]
VO_IO2
VO_IO1
VO_CLK
XX
D0
D1
D2
D3
D4
D5
Dk
XX
DATA_VALID
Figure 7-29. EVO Data-Streaming mode
4
19 20
265 266
283
1
4
One Frame
One Line
Field 2
Field 1
Blanking
Active Video
Vertical
Sync
Video
Lines
NTSC
PAL
263 264
282
525
3
Blanking
23
310 311
312 313
335 336
623 624 625 1
22
1
VO_IO2
Figure 7-30. EVO VO_IO2 timing in FIELD_SYNC mode
if alpha[7] = 1
then output[7:0] = overlay[7:0]
else
output[7:0] = (alpha[6:0] * overlay[7:0] + (alpha[6:0] + 1) * image[7:0]) >> 7
or
output[7:0] = (alpha[6:0] * ( overlay[7:0] - image[7:0] ) >> 7) + image[7:0]