UM10360 Datasheet, PDF (26/835 Pages) NXP Semiconductors – LPC17xx User manual

NXP Semiconductors
UM10360
Chapter 3: LPC17xx System control
Table 11. External Interrupt Mode register (EXTMODE - address 0x400F C148) bit
description
Bit Symbol
Value Description
0 EXTMODE0 0
1
1 EXTMODE1 0
1
2 EXTMODE2 0
1
3 EXTMODE3 0
1
31:4 -
-
Level-sensitivity is selected for EINT0.
EINT0 is edge sensitive.
Level-sensitivity is selected for EINT1.
EINT1 is edge sensitive.
Level-sensitivity is selected for EINT2.
EINT2 is edge sensitive.
Level-sensitivity is selected for EINT3.
EINT3 is edge sensitive.
Reserved, user software should not write ones to reserved
bits. The value read from a reserved bit is not defined.
Reset
value
0
0
0
0
NA
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 Section 8–5) 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 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 0
EXTMODE0).
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 0
EXTMODE1).
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 0
EXTMODE2).
1
EINT2 is high-active or rising-edge sensitive (depending on
EXTMODE2).
UM10360_1
User manual
Rev. 01 — 4 January 2010
© NXP B.V. 2010. All rights reserved.
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