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UM10601
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Preliminary user manual
Rev. 1.0 — 7 November 2012
25 of 313
NXP Semiconductors
UM10601
Chapter 4: LPC800 System configuration (SYSCON)
4.6.12 System clock divider register
This register controls how the main clock is divided to provide the system clock to the
core, memories, and the peripherals. The system clock can be shut down completely by
setting the DIV field to zero.
4.6.13 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 17.
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.
0x01
31:8
-
Reserved
-
Table 18.
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+ core clocks, 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
RAM
Enables clock for SRAM.
1
0
Disable
1
Enable
3
FLASHREG
Enables clock for flash register interface.
1
0
Disable
1
Enable
4
FLASH
Enables clock for flash.
1
0
Disable
1
Enable
5
I2C
Enables clock for I2C.
0
0
Disable
1
Enable