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 Section 4–5 “Wakeup timer 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 Figure 3–10.
Table 27. External Interrupt Polarity register (EXTPOLAR - address 0xE01F C14C) bit
description
Bit Symbol Value Description Reset
value
0EXTPOLAR00 EINT0
is low-active or falling-edge sensitive (depending on
EXTMODE0). 0
1EINT0
is high-active or rising-edge sensitive (depending on
EXTMODE0).
1EXTPOLAR10 EINT1
is low-active or falling-edge sensitive (depending on
EXTMODE1). 0
1EINT1
is high-active or rising-edge sensitive (depending on
EXTMODE1).
2EXTPOLAR20 EINT2
is low-active or falling-edge sensitive (depending on
EXTMODE2). 0
1EINT2
is high-active or rising-edge sensitive (depending on
EXTMODE2).
3EXTPOLAR30 EINT3
is low-active or falling-edge sensitive (depending on
EXTMODE3). 0
1EINT3
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