External interrupts

[lseletron]

Posted on February 16, 2007 at 11:16

External interrupts

[lseletron]

Posted on February 16, 2007 at 06:29

Hi,

I am using ST72F325. How can I select which pin is to be the source of an external interrupt? This chip does not have a register like the EISR register in the LITE chips. Thanks

[pjr]

Posted on February 16, 2007 at 09:34

There are specific pins which can be used as external interrupts. Table 1 of the datasheet indicates which pins have interrupt capability and which external interrupt ( eix ) each of these pins can be connected to.

The ports DDR and OR registers are used to configure a pin for interrupt use. See datasheet section 9.5.1 for this information. pjr

[philippe2]

Posted on February 16, 2007 at 11:16

There is no way in the ST7F325 to select one pin in a group sharing the same interrupt as in ST7FLITE.

You select which pin will generate an interrupt with the option register. If option register bit is 0, pin configuration is floating and no interrupt will be generated. If option register bit is 1, an interrupt will be generated, pin configuration is floating or pull-up depending on the pin. See table 12, port configuration. If you need pull up without interrupt on a pin of a group sharing an interrupt, you have to add an external resistor. This scheme enables to have more interrupt pins than on the ST7FLITE.