Philips Semiconductors
Preliminary specification
PAL/NTSC/SECAM video decoder with adaptive PAL/NTSC
comb filter, VBI-data slicer and high performance scaler
SAA7114H
8.6
Audio clock generation
• Audio master Clocks Nominal Increment,
(subaddresses 30H to 3FH)
ACNI[21:0]36H[5:0]35H[7:0]34H[7:0] according to the
audio frequency
crystal frequency
× 2 23
SAA7114H incorporates generation of a field locked audio
clock, as an auxiliary function for video capture. An audio
sample clock, that is locked to the field frequency, makes
sure that there is always the same predefined number of
audio samples associated with a field, or a set of fields.
That ensures synchronous playback of audio and video
after digital recording (e.g. capture to hard disk), MPEG or
other compression, or non-linear editing.
equation: ACNI21:0] = round
--------------------------------------------
See Table 21 for examples.
Remark: For standard applications the synthesized audio
clock AMCLK can be used directly as master clock and as
input clock for port AMXCLK (short cut) to generate
ASCLK and ALRCLK. For high-end applications it is
recommended to use an external analog PLL circuit to
enhance the performance of the generated audio clock.
8.6.1
MASTER AUDIO CLOCK
The audio clock is synthesized from the same crystal
frequency as the line-locked video clock is generated.
The master audio clock is defined by the parameters:
• Audio master Clocks Per Field,
ACPF[17:0]32H[1:0]31H[7:0]30H[7:0] according to the
audio frequency
field frequency
equation: ACPF[17:0] = round
------------------------------------------
Table 21 Programming examples for audio master clock generation
ACPF
ACNI
XTALO (MHz)
FIELD (Hz)
DECIMAL
HEX
DECIMAL
HEX
AMCLK = 256 × 48 kHz (12.288 MHz)
50
245760
3C000
3210190
30FBCE
32.11
59.94
205005
320CD
3210190
30FBCE
50
−
−
−
−
−
−
−
−
24.576
59.94
AMCLK = 256 × 44.1 kHz (11.2896 MHz)
50
225792
188348
225792
188348
37200
2DFBC
37200
2949362
2949362
3853517
3853517
2D00F2
2D00F2
3ACCCD
3ACCCD
32.11
59.94
50
24.576
59.94
2DFBC
AMCLK = 256 × 32 kHz (8.192 MHz)
50
163840
136670
163840
136670
28000
215DE
28000
215DE
2140127
2140127
2796203
2796203
20A7DF
20A7DF
2AAAAB
2AAAAB
32.11
59.94
50
24.576
59.94
2000 Mar 15
58
NXP [ NXP ]
