External Interrupts; Block Diagram; Connection Diagram; Figure 2-1: External Interrupts Block Diagram - Fujitsu ALL Series Application Note

2 External Interrupts

THE BASIC FUNCTIONALITY OF THE EXTERNAL INTERRUPT MODULE

2.1 Block Diagram

Figure 2-1 shows the internal block diagram of an External Interrupt channel.
Pin INTn

2.2 Connection Diagram

Figure 2-2 shows the connection diagram depicting how the external interrupt pin INTn is
interfaced to the external circuitry.
The pull up resistor R is connected to limit the current when the key is pressed. The
capacitor (hardware debounce) circuit shown with the dotted line is optional and is used to
eliminate the bouncing of the switch. The RC time constant needs to be chosen according to
the bouncing time or debounce delay of the switch. If such arrangement is not used then the
bouncing needs to be taken care in the software and also vice a versa.
Here the INTn needs to be configured to detect a falling edge.
MCU-AN -300203-E-V17
EXTERNAL INTERRUPTS
Chapter 2 External Interrupts
MCU
Detection

Figure 2-1: External Interrupts Block Diagram

Vcc
R
INTn
C

Figure 2-2: External Interrupts Connection Diagram

Edge
Circuit
MCU
- 6 - © Fujitsu Microelectronics Europe GmbH
Interrupt
Request