DR
AFT
DR
AFT
DRAFT
DR
D
RAFT
DRAFT
DRA
FT DRAF
D
RAFT DRAFT DRAFT DRAFT DRAFT D
DRAFT
D
RAFT DRA
FT DRAFT DRAFT DRAFT DRA
UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
37 of 571
NXP Semiconductors
UM10316
Chapter 3: LPC29xx Clock Generation Unit (CGU)
5.3 Crystal-oscillator status register (CGU0)
The register XTAL_OSC_STATUS reflects the status bits for the crystal oscillator.
5.4 Crystal oscillator control register (CGU0)
The register XTAL_OSC_CONTROL contains the control bits for the crystal oscillator.
Following a change of ENABLE bit in XTAL_OSC_CONTROL register requires a read in
XTAL_OSC_STATUS to confirm ENABLE bit is indeed changed.
2
PLL_PRESENT
R
Activity-detection register for normal PLL
output
1*
Clock present
0
Clock not present
1
XTAL_PRESENT
(CGU0) or
BASE_ICLK0_CLK_
PRESENT (CGU1)
R
Activity-detection register for crystal
-oscillator output
1*
Clock present
0
Clock not present
0
LP_OSC_PRESEN
T (CGU0) or
BASE_ICLK1_CLK_
PRESENT (CGU1)
R
Activity-detection register for LP_OSC
1*
Clock present
0
Clock not present
Table 16.
RDET register bit description (RDET, address 0xFFFF 8018 (CGU0) or 0xFFFF
B018 (CGU1))
…continued
* = reset value
Bit
Symbol
Access
Value
Description
Table 17.
XTAL_OSC_STATUS register bit description (XTAL_OSC_STATUS, address
0xFFFF 801C)
* = reset value
Bit
Symbol
Access
Value
Description
31 to 3
reserved
R
-
Reserved
2
HF
R
Oscillator HF pin
1*
Oscillator high-frequency mode (crystal or
external clock source above 10 MHz)
0
Oscillator low-frequency mode (crystal or
external clock source below 20 MHz)
1
BYPASS
R
Configure crystal operation or external clock
input pin XIN_OSC
0
Operation with crystal connected
1*
Bypass mode. Use this mode when an external
clock source is used instead of a crystal
0
ENABLE
R
Oscillator-pad enable
0
Power-down
1*
Enable