Appendix E HDTV Output Mode
CX25870/871
E.5 Automatic Trilevel Sync Generation
Flicker-Free Video Encoder with Ultrascale Technology
The table below summarizes the different permutations of the
RASTER_SEL[1:0] bits and the resolutions/modes supported with each option.
Table E-4. CX25870/CX25871 RASTER_SEL[1:0] Bit Functionality
RASTER_SEL RASTER_SEL
HDTV/ATSC Mode
LOWSYNC period (ns)
HIGHSYNC period (ns)
[1]
[0]
1080i = SMPTE 274M (1)
1
1
44 clock periods =
592.6 ns
44 clock periods =
592.6 ns
720p = SMPTE 296M(2)
480p = SMPTE 293M
1
0
0
1
40 clock periods = 538.7ns 40 clock periods = 538.7ns
63 clock periods =
No HIGHSYNC period
2.36 µs.
0
0
Trilevel sync periods dictated by
HSYNC*&VSYNC* input levels
LOWSYNC period = width
of VSYNC* input
HIGHSYNC period = width
of HSYNC* input
NOTE(S):
(1)
The CX25870/871 can also be programmed for EIA-770.3 1080i format compliance. To do so, set RASTER_SEL[1:0] = 11 and
set the BPB_SYNC_DIS and RPR_SYNC_DIS bits to 1 to disable the trilevel sync on the PB and PR signals.
The CX25870/871 can also be programmed for EIA-770.3 720p format compliance. To do so, set RASTER_SEL[1:0] = 10 and
set the BPB_SYNC_DIS and RPR_SYNC_DIS bits to 1 to disable the trilevel sync on the PB and PR signals.
To obtain any of these SMPTE specifications, visit Global Engineering Documents at: http://global.ihs.com/
(2)
(3)
The inserted syncs will adhere to Figure 3 and the analog and digital timing
relationships found in the various SMPTE specifications. All lines of the First and
Second Fields of an Interlaced System will contain the trilevel syncs. This
includes lines #1-5 and #564-567 of the 1080i format. Line 563 is an
extraordinary case and the reader should defer to the SMPTE 274M specification
for more details on this topic.
An illustration of the typical trilevel sync output from the CX25870/871is
shown on the next page. Note that the CX25870/871 cannot transmit negative
voltages. As a result, the video output is offset by +350mV to accommodate the
negative sync levels listed in the governing specifications.
E-10
Conexant
100381B
CONEXANT [ CONEXANT SYSTEMS, INC ]
