I_OSC raised unexpectedly during Wake Up mode

[LltWc]

I've been implementing Wake Up mode with inductive wakeup on the ST25R3916 with custom firmware. It's all functioning as expected, except for the oscillator interrupt.

As seen in the logs below, when I switch to Wake Up mode, I mask every IRQ except I_WAM and I_WPH. Just to be safe, I added a readout. The Wake Up timer is configured to take a measurement every 100ms. But every 100ms, it sends an I_OSC interrupt when it switches to Ready to take amplitude and phase measurements. Why would this occur? Is there something beyond just M_OSC being set that I need to do?

 

 

[Brian TIDAL]

Hi,

as explained in §4.2.5 Wake-up mode of the ST25R3916 datasheet, the reader field is activated for an extremely short time to allow phase or amplitude measurements during wake-up mode. Thus, the oscillator is enabled during this short time and I_osc is triggered when the oscillator is stable. 

This is a normal behavior.

Rgds

BT

[LltWc]

Hi Brian, yes, I am aware that the oscillator is enabled in order to take inductive measurements. Why is the interrupt still being raised when I have the mask set?

[Brian TIDAL]

Hi,

see §4.3.1:

"If an interrupt from a certain source is not required it can be disabled by setting the
corresponding bit in the Mask interrupt registers. In case of masking a certain interrupt
source the IRQ line is not set high, but the interrupt status bit is still set in IRQ status
registers."

Rgds

BT