Philips LPC2129 - Table 18: External Interrupt Polarity Register (EXTPOLAR - 0 Xe01 Fc14 C)

System Control Block 72 May 03, 2004
Philips Semiconductors Preliminary User Manual
LPC2119/2129/2194/2292/2294ARM-based Microcontroller
Multiple External Interrupt Pins
Software can select multiple pins for each of EINT3:0 in the Pin Select registers, which are described in chapter Pin Connect
Block on page 126. The external interrupt logic for each of EINT3:0 receives the state of all of its associated pins from the pins’
receivers, along with signals that indicate whether each pin is selected for the EINT function. The external interrupt logic handles
the case when more than one pin is so selected, differently according to the state of its Mode and Polarity bits:
• In Low-Active Level Sensitive mode, the states of all pins selected for EINT functionality are digitally combined using a positive
logic AND gate.
• In High-Active Level Sensitive mode, the states of all pins selected for EINT functionality are digitally combined using a positive
logic OR gate.
• In Edge Sensitive mode, regardless of polarity, the pin with the lowest GPIO port number is used. (Selecting multiple EINT pins
in edge-sensitive mode could be considered a programming error.)
The signal derived by this logic is the EINTi signal in the following logic schematic (Figure 14).
When more than one EINT pin is logically ORed, the interrupt service routine can read the states of the pins from GPIO port using
IO0PIN0 and IO1PIN registers, to determine which pin(s) caused the interrupt.
Table 18: External Interrupt Polarity Register (EXTPOLAR - 0xE01FC14C)
EXTPOLAR Function Description
Reset
Value
0 EXTPOLAR0
When 0, EINT0 is low-active or falling-edge sensitive (depending on EXTMODE0).
When 1, EINT0 is high-active or rising-edge sensitive (depending on EXTMODE0).
0
1 EXTPOLAR1
When 0, EINT1 is low-active or falling-edge sensitive (depending on EXTMODE1).
When 1, EINT1 is high-active or rising-edge sensitive (depending on EXTMODE1).
0
2 EXTPOLAR2
When 0, EINT2 is low-active or falling-edge sensitive (depending on EXTMODE2).
When 1, EINT2 is high-active or rising-edge sensitive (depending on EXTMODE2).
0
3 EXTPOLAR3
When 0, EINT3 is low-active or falling-edge sensitive (depending on EXTMODE3).
When 1, EINT3 is high-active or rising-edge sensitive (depending on EXTMODE3).
0
7:4 Reserved
Reserved, user software should not write ones to reserved bits. The value read from
a reserved bit is not defined.
NA