UM10462
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© NXP B.V. 2016. All rights reserved.
User manual
Rev. 5.5 — 21 December 2016
24 of 523
NXP Semiconductors
UM10462
Chapter 3: LPC11U3x/2x/1x System control block
3.5.4 System PLL status register
This register is a Read-only register and supplies the PLL lock status (see
3.5.5 USB PLL control register
The USB PLL is identical to the system PLL and is used to provide a dedicated clock to
the USB block if available (see
).
This register connects and enables the USB PLL and configures the PLL multiplier and
divider values. The PLL accepts an input frequency from 10 MHz to 25 MHz from various
clock sources. The input frequency is multiplied up to a high frequency, then divided down
to provide the actual clock 48 MHz clock used by the USB subsystem.
Remark:
The USB PLL must be connected to the system oscillator for correct USB
operation (see
).
Table 9.
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 10.
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
-