
UM10237_2
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 02 — 19 December 2008
32 of 792
NXP Semiconductors
UM10237
Chapter 3: LPC24XX System control
3.2 Reset
Reset has four sources on the LPC2400: the RESET pin, the Watchdog Reset, Power On
Reset (POR) and the Brown Out Detection circuit (BOD). The RESET pin is a Schmitt
trigger input pin. Assertion of chip Reset by any source, once the operating voltage attains
a usable level, starts the Wakeup Timer (see description in
this chapter), causing reset to remain asserted until the external Reset is de-asserted, the
oscillator is running, a fixed number of clocks have passed, and the flash controller has
completed its initialization. The reset logic is shown in
Table 27.
External Interrupt Polarity register (EXTPOLAR - address 0xE01F C14C) bit
description
Bit Symbol
Value Description
Reset
value
0
EXTPOLAR0 0
EINT0 is low-active or falling-edge sensitive (depending on
EXTMODE0).
0
1
EINT0 is high-active or rising-edge sensitive (depending on
EXTMODE0).
1
EXTPOLAR1 0
EINT1 is low-active or falling-edge sensitive (depending on
EXTMODE1).
0
1
EINT1 is high-active or rising-edge sensitive (depending on
EXTMODE1).
2
EXTPOLAR2 0
EINT2 is low-active or falling-edge sensitive (depending on
EXTMODE2).
0
1
EINT2 is high-active or rising-edge sensitive (depending on
EXTMODE2).
3
EXTPOLAR3 0
EINT3 is low-active or falling-edge sensitive (depending on
EXTMODE3).
0
1
EINT3 is high-active or rising-edge sensitive (depending on
EXTMODE3).
7:4 -
-
Reserved, user software should not write ones to reserved
bits. The value read from a reserved bit is not defined.
NA