
DR
AFT
DR
AFT
DRAFT
DR
D
RAFT
DRAFT
DRA
FT DRAF
D
RAFT DRAFT DRAFT DRAFT DRAFT D
DRAFT
D
RAFT DRA
FT DRAFT DRAFT DRAFT DRA
UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
22 of 808
NXP Semiconductors
UM10360
Chapter 3: LPC17xx System control
Note: Software should only change a bit in this register when its interrupt is
disabled in the NVIC (state readable in the ISERn/ICERn registers), and should write
the corresponding 1 to EXTINT before enabling (initializing) or re-enabling the
interrupt. An extraneous interrupt(s) could be set by changing the mode and not
having the EXTINT cleared.
6.4 External Interrupt Polarity register (EXTPOLAR - 0x400F C14C)
In level-sensitive mode, the bits in this register select whether the corresponding pin is
high- or low-active. In edge-sensitive mode, they select whether the pin is rising- or
falling-edge sensitive. Only pins that are selected for the EINT function Only pins that are
selected for the EINT function (see
) and enabled in the appropriate NVIC
register) can cause interrupts from the External Interrupt function (though of course pins
selected for other functions may cause interrupts from those functions).
Note: Software should only change a bit in this register when its interrupt is
disabled in the NVIC (state readable in the ISERn/ICERn registers), and should write
the corresponding 1 to EXTINT before enabling (initializing) or re-enabling the
interrupt. An extraneous interrupt(s) could be set by changing the polarity and not
having the EXTINT cleared.
Table 11.
External Interrupt Mode register (EXTMODE - address 0x400F C148) bit
description
Bit
Symbol
Value
Description
Reset
value
0
EXTMODE0 0
Level-sensitivity is selected for EINT0.
0
1
EINT0 is edge sensitive.
1
EXTMODE1 0
Level-sensitivity is selected for EINT1.
0
1
EINT1 is edge sensitive.
2
EXTMODE2 0
Level-sensitivity is selected for EINT2.
0
1
EINT2 is edge sensitive.
3
EXTMODE3 0
Level-sensitivity is selected for EINT3.
0
1
EINT3 is edge sensitive.
7:4
-
-
Reserved, user software should not write ones to reserved
bits. The value read from a reserved bit is not defined.
NA
Table 12.
External Interrupt Polarity register (EXTPOLAR - address 0x400F 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).