UM10208_2
© NXP B.V. 2007. All rights reserved.
User manual
Rev. 02 — 1 June 2007
58 of 362
NXP Semiconductors
UM10208
Chapter 7: LPC2800 CGU
3.5.1 Memory Table Mapping
In this method, the application must include three tables called NTAB, MTAB, and PTAB in
memory, the contents of which were calculated by a standalone program as part of the
development of the LPC288x. In order to obtain the specific register values, software must
use the desired xSEL value as an index into the corresponding memory table, and extract
the register values as shown in
.
3.5.2 Manual Memory Table Lookup
Some applications may not have room in memory for the tables used in the previous
method (particularly MTAB). In this case, for each multiplier or divisor required by the
application, obtain the files that can be used as memory tables as described above, look
up each desired xSEL value in the files (comments identify the indices), and extract the
associated control register values.
3.5.3 Common HP PLL Applications
shows multiplier and divisor values that derive common frequencies from the
Fast oscillator running at 12 MHz, with the associated values for the HPNDEC, HPMDEC,
HPPDEC, HPSELR, HPSELI, and HPSELP registers. All values are decimal.
Table 40.
HS PLL Multiplication and Division Memory Tables
Memory
table
Indexed
by
index
bits
output
bits
Write to register(s)
Table size
NTAB
NSEL
8
10 HPNDEC
256 halfwords
(512 bytes)
MTAB
MSEL
15
30 HPMDEC, HPSELR, HPSELI, HPSELP 32k words
(128k bytes)
PTAB
PSEL
5
7 HPPDEC
32 bytes
Table 41.
Common HP PLL Applications (Fin = 12 MHz)
Init
div
Mul in
(MHz)
Mult
Mul out
(MHz)
Final
div
Out
(MHz)
NDEC
MDEC
PDEC
SELR SELI
SELP
25
0.48
588
282.24
50
5.6448
63
2880
6
2
4
31
5
2.4
128
307.20
50
6.144
5
34
6
0
15
31
75
0.16 2048
327.68
40
8.192
102
8194
31
7
2
31
61
0.197 2066
406.43
36
11.2896
131
1408
7
8
2
31
25
0.48
768
368.64
30
12.288
63
16973
24
2
3
31
75
0.16 2048
327.68
20
16.384
102
8194
14
7
2
31
61
0.197 2066
406.43
18
22.5792
131
1408
23
8
2
31
25
0.48 1024
491.52
20
24.576
63
16416
14
3
2
31
75
0.16 2048
327.68
10
32.768
102
8194
5
7
2
31
87
0.138 3274
451.59
10
45.158
251
9099
5
12
2
31
25
0.48 1024
491.52
10
49.152
63
16416
5
3
2
31