
TM1300 Data Book
Philips Semiconductors
7-6
PRODUCT SPECIFICATION
avoided in the video data output by the EVO to prevent
accidental generation of an invalid sync code. The EVO
provides programmable maximum and minimum value
clipping on the video data to prevent this possibility. If
clipping is enabled, the EVO automatically clips the re-
sulting image data as described in Section 7.15.3.
7.8.5
CCIR 656 Frame Timing
The interlaced frame timing defined by CCIR 656 is
shown in Table 7-3. Lines are numbered from 1 to 525
for 525-line, 60-Hz systems and from 1 to 625 for 625-
line, 50-Hz systems. The Field and Vertical Blanking col-
umns indicate whether the field and vertical blanking bits,
respectively, are set in the SAV and EAV codes for the
indicated lines. The 525 and 625 formats have similar
timing but differ in their line numbering.
7.9
ENHANCED VIDEO OUT TIMING
GENERATION
The EVO generates timing for frames, active video areas
within frames, images within the active video area, and
overlays within the image area. The relationship between
these four is shown in Figure 7-13. The frame includes
the timing for both interlaced fields. Progressive scan, or
non-interlaced video, is accomplished by setting the tim-
ing parameters such that two identical successive fields
are generated.
7.9.1
Active Video Area
Shown in Figure 7-13, the active video area begins after
the horizontal and vertical blanking intervals and repre-
sents the pixels visible on the screen. The image area is
the actual displayed image within the active video area.
It can be slightly smaller than the active video area to
avoid edge effects at the top, bottom and sides of the im-
age. The overlay area is within the image area.
The EVO uses counters to generate and control image
timing. The Frame Line Counter and Frame Pixel
Counter control the overall timing for the frame and de-
fine the total number of pixels per line, lines per frame,
and interlace timing, including horizontal and vertical
blanking intervals.
Note that the Frame Line Counter has a starting value of
one, not zero, and it counts from 1 to 525 or 625, consis-
tent with CCIR 656 line numbering. The Image Line
Table 7-2. SAV and EAV codes
Code
Binary Value
Field
Vertical Blanking
SAV
1000 0000
1
EAV
1001 1101
1
SAV
1010 1011
1
X
EAV
1011 0110
1
X
SAV
1100 0111
2
EAV
1101 1010
2
SAV
1110 1100
2
X
EAV
1111 0001
2
X
Table 7-3. CCIR 656 frame timing
Line Number
F bit
V bit
Comments
525/60
625/50
1–3
624–625
1
Vertical blanking for
Field 1, SAV/EAV
code still indicates
Field 2
4–19
1–22
0
1
Vertical blanking for
Field 1, change
SAV/EAV code to
Field 1
20–263
23–310
0
Active video, Field 1
264–265
311–312
0
1
Vertical blanking for
Field 2, SAV/EAV
code still indicates
Field 1
266–282
313–335
1
Vertical blanking for
Field 2, change
SAV/EAV code to
Field 2
283–525
336–623
1
0
Active video, Field 2
Overlay
Image Area, Field 1
Vertical Blanking, Field 1
Horizontal
Blanking
Overlay
Image Area, Field 2
Vertical Blanking, Field 2
Horizontal
Blanking
Image V Offset
Image
H
Offset
Image
H
Offset
Image Width
Image
Height
Frame
Active Video Area
Start Pixel
Start
Line
Figure 7-13. Active Video Area and Image Area in re-
lation to vertical and horizontal blanking intervals.