Broadcom BCM7405, Общее руководство пользователя

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2/24/2008 9T6WP
Preliminary Hardware Data Module BCM7405
06/29/07
Functional Description
Bro a d c o m Co rp o r a ti o n
Document 7405-1HDM00-R RF Modulator Page 1-57
- Programmable Nicam carrier (DQPSK modulated) level with frequency selectable between 5.85 MHz and 6.5 MHz.
The Nicam carrier can also be transmitted simultaneously with the mono/main-channel FM carrier.
- Bypassable FM modulation and bypassable channel mixer allows baseband BTSC multiplex output.
- Programmable frequency deviation may be used to adjust the frequency deviation (and volume) of the modulated
FM carrier. No audible pops or clicks are expected when the frequency deviation is changed.
- Independent scaling of the two audio input channels may be used to adjust the relative volume of the two audio
input channels. No audible pops or clicks are expected when the volume levels are changed.
- Audio input channels may be muted (allowing for an unmodulated audio carrier) or swapped.
• Digital Video Processor
- Supports digital video composite sources (NTSC or PAL encoded signals).
- Flexibility allows support for television standards B/G, D/K, H, I, K1, M, and N.
- Programmable video clipping levels prevent overmodulation of the video signal.
- Group delay filter compensates for group delay distortion in the television receiver.
- Audio trap filter reduces video signal content at audio carrier frequencies.
- Programmable video modulation depth.
- Video-to-audio carrier ratio is adjustable.
• RF Modulation and digital-to-analog conversion
- Mixes a sum of baseband composite video signal and FM modulated audio carrier and optional NICAM DQPSK
carrier to a programmable frequency that can be chosen from 0 to 75 MHz. This includes NTSC channels 3 and 4,
for example.
- Bypassable mixing stage allows the D/A converter (DAC) to optionally output the sum of the baseband video
composite and the FM modulated audio along with an optional NICAM carrier. The video composite can be scaled
to zero and the FM and NICAM carriers can be independently scaled to different levels so as to output a sound IF
signal. This allows a simple interface to an external agile modulator.
- Optional X/sinX filter compensates for SinX/X distortion inherent in the digital-to-analog conversion process.
- Integrated PLL and 10-bit DAC.
- Programmable DAC attenuation.
- Programmable DAC sample rate.
T
YPICAL
U
SAGE
M
ODES
Supported Television Standards
The intended purpose of the RFM on the BCM7405 chip is to allow the viewing of an analog RF modulated television signal
on a television by modulating that signal to NTSC Channel 3 (61.25 MHz) or NTSC Channel 4 (67.25 MHz).
The RFM supports NTSC and PAL color standards in conjunction with the monochrome television standards B/G, H, I, M,
and N.
Table 1-14 outlines the modulation standards that are supported by the BCM7405.
Table 1-14: Supported Modulation Standards
Monochrome
Mode Color
Standard Video
Bandwidth Vision FM Sound
Carrier Spacing Vision-NICAM
Carrier Spacing Pre-emphasis
(MONO Transmission)
B/G PAL 5.0 MHz 5.5 MHz 5.85 MHz 50 microseconds
H PAL 5.0 MHz 5.5 MHz 5.85 MHz 50 microseconds
I PAL 5.5 MHz 6.0 MHz 6.552 MHz 50 microseconds
M NTSC / PAL 4.2 MHz 4.5 MHz – 75 microseconds
N PAL 4.2 MHz 4.5 MHz – 75 microseconds