Multiple External Interrupt Pins - Philips LPC214 Series User Manual

Philips Semiconductors
Volume 1

3.5.6 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 75. 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:
The signal derived by this logic processing multiple external interrupt pins is the EINTi
signal in the following logic schematic
For example, if the EINT3 function is selected in the PINSEL0 and PINSEL1 registers for
pins P0.9, P0.20 and P0.30, and EINT3 is configured to be low level sensitive, the inputs
from all three pins will be logically ANDed. When more than one EINT pin is logically
ORed, the interrupt service routine can read the states of the pins from the GPIO port
using the IO0PIN and IO1PIN registers, to determine which pin(s) caused the interrupt.
VPB Bus Data
GLITCH
EINTi
FILTER
EXTPOLARi
EXTMODEi
Write 1 to EXTINTi
Fig 8. External interrupt logic
User manual
•
In Low-Active Level Sensitive mode, the states of all pins selected for the same EINTx
functionality are digitally combined using a positive logic AND gate.
•
In High-Active Level Sensitive mode, the states of all pins selected for the same
EINTx 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 pins for an EINTx in edge-sensitive mode could
be considered a programming error.)
Wakeup enable
(one bit of EXTWAKE)
D Q
PCLK
1
Reset
Rev. 01 — 15 August 2005
Figure 8.
S
D
S
Q
Q
R
R
PCLK
UM10139
Chapter 3: System Control Block
VPB Read
of EXTWAKE
EINTi to
Wakeup Timer
(Figure 11)
Interrupt Flag
(one bit of EXTINT)
S
Q to VIC
R
VPB Read
of EXTINT
PCLK
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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