Table 18: External Interrupt Polarity Register (Extpolar - 0Xe01Fc14C) - Philips LPC2194 User Manual

Philips Semiconductors
ARM-based Microcontroller

Table 18: External Interrupt Polarity Register (EXTPOLAR - 0xE01FC14C)

EXTPOLAR Function
0 EXTPOLAR0
1 EXTPOLAR1
2 EXTPOLAR2
3 EXTPOLAR3
7:4 Reserved
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.
System Control Block
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).
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).
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).
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).
Reserved, user software should not write ones to reserved bits. The value read from
a reserved bit is not defined.
LPC2119/2129/2194/2292/2294
Description
72
Preliminary User Manual
Reset
Value
0
0
0
0
NA
May 03, 2004