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UM10503
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© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
137 of 1269
NXP Semiconductors
UM10503
Chapter 11: LPC43xx Clock Generation Unit (CGU)
11.8.4.2 Bypassing the fractional divider
To bypass the fractional divider and use the MDEC value directly, follow these steps:
1. Set bit SEL_EXT = 1 in the PLL0AUDIO_CTRL register (
2. Calculate NDEC, PDEC, and MDEC for the output frequency Fout.
3. Write the calculated NDEC and PDEC values to the PLL0AUDIO_NP_DIV register.
4. Write the calculated MDEC value to the PLL0AUDIO_MDIV register.
16
16.384
360.448
1
1
29
0x0000101d
0x16872b
12
12.288
417.792
1
1
3
0x00001003
0x1a1cac
11.025
11.2896
338.688
1
0
24
0x00000018
0x070e56
8
8.192
344.064
1
0
30
0x0000001e
0x072b02
Table 95.
PLL0AUDIO divider settings for 12 MHz input
Fs [kHz]
Fout [MHz]
Fcco [MHz] Error [Hz]
NDEC
PDEC PLL0AUDIO_NP_DIV
PLLF0RACT_CTRL
Table 77
Table 78
Table 96.
PLL0AUDIO divider setting for 12 MHz with fractional divider bypassed
Fs
[KHz]
Fout
[MHz]
Fcco
[MHz]
Error
[Hz]
NDEC
MDEC
PDEC
PLL0AUDIO_
MDIV
PLL0AUDIO_
NP_DIV
128 Fs
192
24.576
491.52
0
63
13523
14
0x000034d3
0x0003f00e
96
12.288
368.64
0
63
2665
24
0x00000a69
0x0003f018
88.2
11.2896
338.688
0
45
18810
24
0x0000497a
0x0002d018
64
8.192
409.6
0
61
18724
6
0x00004924
0x0003d006
48
6.144
307.2
0
5
30580
6
0x00007774
0x00005006
44.1
5.6448
282.24
0
63
31356
6
0x00007a7c
0x0003f006
256 Fs
192
49.152
491.52
0
63
13523
5
0x000034d3
0x0003f005
96
24.576
491.52
0
63
13523
14
0x000034d3
0x0003f00e
88.2
22.5792
451.584
0
45
29122
14
0x000071c2
0x0002d00e
64
16.384
491.52
0
63
13523
24
0x000034d3
0x0003f018
48
12.288
368.64
0
63
2665
24
0x00000a69
0x0003f018
44.1
11.2896
338.688
0
45
18810
24
0x0000497a
0x0002d018
32
8.192
409.6
0
61
18724
6
0x00004924
0x0003d006
24
6.144
307.2
0
5
30580
6
0x00007774
0x00005006
22.05
5.6448
282.24
0
63
31356
6
0x00007a7c
0x0003f006
384 Fs
192
73.728
294.912
0
45
4770
66
0x000012a2
0x0002d042
96
36.864
368.64
0
63
2665
5
0x00000a69
0x0003f005
88.2
33.8688
338.688
0
45
18810
5
0x0000497a
0x0002d005
64
24.576
491.52
0
63
13523
14
0x000034d3
0x0003f00e