UM10462
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© NXP B.V. 2016. All rights reserved.
User manual
Rev. 5.5 — 21 December 2016
31 of 523
NXP Semiconductors
UM10462
Chapter 3: LPC11U3x/2x/1x System control block
3.5.18 System clock control register
The SYSAHBCLKCTRL register enables the clocks to individual system and peripheral
blocks. The system clock (bit 0) provides the clock for the AHB, the APB bridge, the ARM
Cortex-M0, the Syscon block, and the PMU. This clock cannot be disabled.
Table 23.
System clock divider register (SYSAHBCLKDIV, address 0x4004 8078) bit
description
Bit
Symbol
Description
Reset
value
7:0
DIV
System AHB clock divider values
0: System clock disabled.
1: Divide by 1.
to
255: Divide by 255.
0x1
31:8
-
Reserved
-
Table 24.
System clock control register (SYSAHBCLKCTRL, address 0x4004 8080) bit
description
Bit
Symbol
Value
Description
Reset
value
0
SYS
Enables the clock for the AHB, the APB bridge, the
Cortex-M0 FCLK and HCLK, SysCon, and the PMU.
This bit is read only and always reads as 1.
1
0
Reserved
1
Enable
1
ROM
Enables clock for ROM.
1
0
Disable
1
Enable
2
RAM0
Enables clock for Main SRAM0.
1
0
Disable
1
Enable
3
FLASHREG
Enables clock for flash register interface.
1
0
Disable
1
Enable
4
FLASHARRAY
Enables clock for flash array access.
1
0
Disable
1
Enable
5
I2C
Enables clock for I2C.
1
0
Disable
1
Enable
6
GPIO
Enables clock for GPIO port registers.
0
0
Disable
1
Enable
7
CT16B0
Enables clock for 16-bit counter/timer 0.
0
0
Disable
1
Enable