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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
27 of 313
NXP Semiconductors
UM10601
Chapter 4: LPC800 System configuration (SYSCON)
4.6.14 USART clock divider register
This register configures the clock for the fractional baud rate generator and all USARTs.
The UART clock can be disabled by setting the DIV field to zero (this is the default
setting).
4.6.15 CLKOUT clock source select register
This register selects the signal visible on the CLKOUT pin. Any oscillator or the main clock
can be selected.
Bit 0 of the CLKOUTUEN register (see
) must be toggled from 0 to 1 for the
update to take effect.
4.6.16 CLKOUT clock source update enable register
This register updates the clock source of the CLKOUT pin with the new clock after the
CLKOUTSEL register has been written to. In order for the update to take effect at the input
of the CLKOUT pin, first write a zero to bit 0 of this register, then write a one.
19
ACMP
Enables clock to analog comparator.
0
0
Disable
1
Enable
31:20 -
-
Reserved
-
Table 18.
System clock control register (SYSAHBCLKCTRL, address 0x4004 8080) bit
description
…continued
Bit
Symbol
Value
Description
Reset
value
Table 19.
USART clock divider register (UARTCLKDIV, address 0x4004 8094) bit description
Bit
Symbol
Description
Reset
value
7:0
DIV
USART clock divider values.
0: Clock disabled.
1: Divide by 1.
to
255: Divide by 255.
0
31:8
-
Reserved
-
Table 20.
CLKOUT clock source select register (CLKOUTSEL, address 0x4004 80E0) bit
description
Bit
Symbol
Value
Description
Reset
value
1:0
SEL
CLKOUT clock source
0
0x0
IRC oscillator
0x1
Crystal oscillator (SYSOSC)
0x2
Watchdog oscillator
0x3
Main clock
31:2
-
-
Reserved
0