UM10503
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
105 of 1269
NXP Semiconductors
UM10503
Chapter 11: LPC43xx Clock Generation Unit (CGU)
11.6.2 Crystal oscillator control register
The register XTAL_OSC_CONTROL contains the control bits for the crystal oscillator.
Table 68.
FREQ_MON register (FREQ_MON, address 0x4005 0014) bit description
Bit
Symbol
Value
Description
Reset
value
Access
8:0
RCNT
9-bit reference clock-counter value
0
R/W
22:9
FCNT
14-bit selected clock-counter value
0
R
23
MEAS
Measure frequency
0
R/W
0
RCNT and FCNT disabled
1
Frequency counters started
28:24
CLK_SEL
Clock-source selection for the clock to be
measured. All other values are reserved.
0
R/W
0x00
32 kHz oscillator (default)
0x01
IRC
0x02
ENET_RX_CLK
0x03
ENET_TX_CLK
0x04
GP_CLKIN
0x05
Reserved
0x06
Crystal oscillator
0x07
PLL0USB
0x08
PLL0AUDIO
0x09
PLL1
0x0A
Reserved
0x0B
Reserved
0x0C
IDIVA
0x0D
IDIVB
0x0E
IDIVC
0x0F
IDIVD
0x10
IDIVE
31:29
-
Reserved
-
-
Table 69.
XTAL_OSC_CTRL register (XTAL_OSC_CTRL, address 0x4005 0018) bit
description
Bit
Symbol
Value
Description
Reset
value
Access
0
ENABLE
Oscillator-pad enable. Do not change the BYPASS
and ENABLE bits in one write-action: this will result
in unstable device operation!
1
R/W
0
Enable
1
Power-down (default)