[En-Nut-Discussion] interrupt sense control for RTL8019AS

Henrik Maier hmlists at focus-sw.com
Tue Sep 19 04:43:53 CEST 2006

PragmaLab wrote:
 > It looks like a level triggered interrupt is replaced by an edge 
 > interrupt the moment the signal is inverted.
 > Somebody knows what it should be, level or edge triggered sense control?

Hello Rob,

I probably can shed some light on this as I introduced the rising edge mode.

For a standard Ethernut hardware the classic level triggered mode should 
be used. This mode is also backwards compatible to the Atmega103 MCU 
which does not support edge triggered interrupts.

The polarity of the level triggered interrupt cannot be changed on the 
ATmega128, but the polarity of an edge triggered interrupt can be 

On our XNUT-100/XNUT-105 hardware design we use the rising edge 
triggered mode for the RTL interrupt which saves use an inverter gate as 
the RTL8019AS interrupt line (INT0) can be connected directly to the 
ATmega128 input pin.

This mode is enabled in the driver by the macro definition 
RTL_IRQ_RISING_EDGE and set in the Nut/OS configurator or in the .conf 

As this works only for hardware designed for rising edge triggered mode, 
it should not be used for a Ethernut 1.3 hardware.

Best Regards


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