Nxp Semiconductors UM10237 Manual De Usuario
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UM10237_2
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 02 — 19 December 2008
44 of 792
NXP Semiconductors
UM10237
Chapter 4: LPC24XX Clocking and power control
Since chip operation always begins using the Internal RC Oscillator, and the main
oscillator may never be used in some applications, it will only be started by software
request. This is accomplished by setting the OSCEN bit in the SCS register, as described
in
oscillator may never be used in some applications, it will only be started by software
request. This is accomplished by setting the OSCEN bit in the SCS register, as described
in
. The main oscillator provides a status flag (the OSCSTAT bit in the SCS
Fig 13. Oscillator modes and models: a) slave mode of operation, b) oscillation mode of operation, c) external
crystal model used for C
X1
/
X2
evaluation
LPC24xx
LPC24xx
Clock
C
C
C
X1
C
X2
C
L
C
P
L
R
S
< = >
a)
b)
c)
Xtal
XTAL1
XTAL2
XTAL1
XTAL2
Table 39.
Recommended values for C
X1/X2
in oscillation mode (crystal and external
components parameters) low frequency mode (OSCRANGE = 0, see
)
Fundamental
oscillation frequency
F
oscillation frequency
F
OSC
Crystal load
capacitance C
capacitance C
L
Maximum crystal
series resistance R
series resistance R
S
External load
capacitors C
capacitors C
X1
,
CX2
1 MHz - 5 MHz
10 pF
< 300
Ω
18 pF, 18 pF
20 pF
< 300
Ω
39 pF, 39 pF
30 pF
< 300
Ω
57 pF, 57 pF
5 MHz - 10 MHz
10 pF
< 300
Ω
18 pF, 18 pF
20 pF
< 200
Ω
39 pF, 39 pF
30 pF
< 100
Ω
57 pF, 57 pF
10 MHz - 15 MHz
10 pF
< 160
Ω
18 pF, 18 pF
20 pF
< 60
Ω
39 pF, 39 pF
15 MHz - 20 MHz
10 pF
< 80
Ω
18 pF, 18 pF
Table 40.
Recommended values for C
X1/X2
in oscillation mode (crystal and external
components parameters) high frequency mode (OSCRANGE = 1, see
Fundamental
oscillation frequency
F
oscillation frequency
F
OSC
Crystal load
capacitance C
capacitance C
L
Maximum crystal
series resistance R
series resistance R
S
External load
capacitors C
capacitors C
X1
,
CX2
15 MHz - 20 MHz
10 pF
< 180
Ω
18 pF, 18 pF
20 pF
< 100
Ω
39 pF, 39 pF
20 MHz - 25 MHz
10 pF
< 160
Ω
18 pF, 18 pF
20 pF
< 80
Ω
39 pF, 39 pF