Datasheet
If filtering or edge detection is enabled, the EIC automatically requests the GCLK_EIC to operate
(GCLK_EIC must be enabled in the GCLK module, see GCLK – Generic Clock Controller for details). If
level detection is enabled, GCLK_EIC is not required, but interrupt and events can still be generated.
When an external interrupt is configured for level detection and when filtering is disabled, detection is
done asynchronously. Asynchronuous detection does not require GCLK_EIC, but interrupt and events
can still be generated. If filtering or edge detection is enabled, the EIC automatically requests GCLK_EIC
to operate. GCLK_EIC must be enabled in the GCLK module.
Figure 21-2. Interrupt Detections
intreq_extint[x]
(edge detection / filter)
intreq_extint[x]
(edge detection / no filter)
intreq_extint[x]
(level detection / filter)
intreq_extint[x]
(level detection / no filter)
EXTINTx
CLK_EIC_APB
GCLK_EIC
clear INTFLAG.EXTINT[x]
No interrupt
No interrupt
The detection delay depends on the detection mode.
Table 21-2. Interrupt Latency
Detection mode Latency (worst case)
Level without filter Three CLK_EIC_APB periods
Level with filter Four GCLK_EIC periods + Three CLK_EIC_APB periods
Edge without filter Four GCLK_EIC periods + Three CLK_EIC_APB periods
Edge with filter Six GCLK_EIC periods + Three CLK_EIC_APB periods
Related Links
15. GCLK - Generic Clock Controller
21.6.4 Additional Features
21.6.4.1 Non-Maskable Interrupt (NMI)
The non-maskable interrupt pin can also generate an interrupt on edge or level detection, but it is
configured with the dedicated NMI Control register (NMICTRL). To select the sense for NMI, write to the
NMISENSE bit group in the NMI Control register (NMICTRL.NMISENSE). NMI filtering is enabled by
writing a '1' to the NMI Filter Enable bit (NMICTRL.NMIFILTEN).
If edge detection or filtering is required, enable GCLK_EIC or CLK_ULP32K.
NMI detection is enabled only by the NMICTRL.NMISENSE value, and the EIC is not required to be
enabled.
SAM D21 Family
EIC – External Interrupt Controller
© 2018 Microchip Technology Inc.
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