cx25840 Conexant Systems, Inc., cx25840 Datasheet - Page 115

• Manufacturer Part Number: cx25840
• Description: Video Decoder And Broadcast Audio
• Manufacturer: Conexant Systems, Inc.

CX25840/1/2/3 Data Sheet
102284B
8/3/05
initially available it will try to detect A2-BG. If the microcontroller detects a NICAM
or A2-BG signal, it will be played. If some other signal, say in this example, A2-DK is
present, then the audio will mute. This mode is programmed by setting
AUD_STANDARD to 0xF and AUD_MODE/AUD_SYSTEM to the appropriate
system.
The third level of auto-detection is worldwide where all TV audio standards except
FM Radio, AF FM Radio, and AF BTSC are auto-detected in real-time. Once the
standard has been decided on, the mode is then auto-detected. This configuration
includes carrier detection, meaning if the carrier goes away, a redetection will occur.
To put the microcontroller in worldwide auto-detection mode, AUD_STANDARD is
set to 0xF and AUD_MODE/AUD_SYSTEM is set to 0xF.
To program the audio core for a forced audio standard and forced mode, for example
NICAM-BG stereo, program the following registers:
To program audio core for worldwide TV audio auto-standard and mode detection,
program the following registers:
To program audio core for system auto-standard and mode detection, for example A2-
M, program the following registers:
1.
2.
1.
2.
3.
4.
5.
6.
7.
Set AUD_STANDARD in Audio Configuration (0x808) register to 0xA
Set AUD_MODE/AUD_SYSTEM in register Audio Configuration (0x808) to
0x4.
Set FORMAT_45MHZ in Audio Format Control (0x80B) register to:
a.
b.
c.
d.
e.
Set FORMAT_65MHZ in Audio Format Control (0x80B) register to:
a.
b.
c.
Set FM_DEVIATION in Preferred Decode Mode (0x809) register to:
a.
b.
c.
Set PREF_MODE in Preferred Decode Mode (0x809) register to:
a.
b.
c.
Set MUTE_NO_PREF_MODE in Preferred Decode Mode (0x809) register to:
a.
b.
Set AUD_STANDARD in Audio Configuration (0x808) register to 0xF
Set AUD_SYSTEM in Audio Configuration (0x808) register to 0xF
0x000—4.5 MHz carrier to be interpreted as Chroma (default)
0x001–4.5 MHz carrier to be interpreted as BTSC
0x010—4.5 MHz carrier to be interpreted as EIAJ
0x011—4.5 MHz carrier to be interpreted as A2-M
0x100—4.5 MHz carrier to be auto-detected
0x00—6.5 MHz carrier to be interpreted as System DK (default)
0x01—6.5 MHz carrier to be interpreted as System L
0x10—6.5 MHz carrier to be auto-detected
0x0—for normal FM (default)
0x1—for a high deviation signal (up to 384 kHz)
0x2—for a very high deviation signal (up to 540 kHz).
0x0-0x3—for Mono1 (Language A or Mono), Mono2 (Language B), Mono3
(Language C), Mono4 (Analog Fallback)
0x4—for Stereo
0x5-0x7—Dual1 (AC), Dual2 (BC), Dual3 (AB)
0x0—the microcontroller selects the best audio program based on the
preferred mode (i.e., if the preferred mode is language B and stereo is the
detected mode, stereo will be played).
0x1—the microcontroller will mute the audio if the preferred mode is not
available (i.e., if the preferred mode is language B and stereo is the detected
mode, audio will be muted.
Conexant
Detailed Functional Description
3-89