UM11029
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© NXP Semiconductors N.V. 2017. All rights reserved.
User manual
Rev. 1.0 — 16 June 2017
90 of 515
NXP Semiconductors
UM11029
Chapter 8: LPC84x System configuration (SYSCON)
8.6.3 System PLL status register
This register is a Read-only register and supplies the PLL lock status (see
8.6.4 System oscillator control register
This register configures the frequency range for the system oscillator. The system
oscillator itself is powered on or off in the PDRUNCFG register. See
Table 127. System PLL control register (SYSPLLCTRL, address 0x4004 8008) bit description
Bit
Symbol
Value
Description
Reset
value
4:0
MSEL
Feedback divider value. The division value M is the
programmed MSEL value + 1.
00000: Division ratio M = 1
to
11111: Division ratio M = 32
0
6:5
PSEL
Post divider ratio P. The division ratio is 2
P.
0
0x0
P = 1
0x1
P = 2
0x2
P = 4
0x3
P = 8
31:7
-
-
Reserved. Do not write ones to reserved bits.
-
Table 128. System PLL status register (SYSPLLSTAT, address 0x4004 800C) bit description
Bit
Symbol
Value
Description
Reset
value
0
LOCK
PLL lock status
0
0
PLL not locked
1
PLL locked
31:1
-
-
Reserved
-
Table 129. System oscillator control register (SYSOSCCTRL, address 0x4004 8020) bit
description
Bit
Symbol
Value
Description
Reset
value
0
BYPASS
Bypass system oscillator
0x0
0
Disabled. Oscillator is not bypassed.
1
Enabled. PLL input (sys_osc_clk) is fed directly
from the XTALIN pin bypassing the oscillator. Use
this mode when using an external clock source
instead of the crystal oscillator.
1
FREQRANGE
Determines oscillator frequency range.
0x0
0
1 - 20 MHz frequency range.
1
15 - 25 MHz frequency range
31:2
-
-
Reserved
0x00