TIC12400-Q1: Using the msdi as wake-up source for MCU

Hi Roberto,

Yes, the device will sample the voltage on all enabled Input Pins once every "polling cycle."  The polling cycle time is configurable, but the fastest cycle time is 2ms.  This means that the shortest interval between sampling the input pins to check for a voltage state change (wake up event) is once every 2ms. 

Also note that the time needed to sample the voltage on each INx pin is only 18-24us, and this is one one pin at a time in sequential order during the polling cycle.  Therefore, to ensure you catch your wake up event on the INx pin, the pin voltage must remain at the new level for a time greater than the polling cycle (i.e. >2ms) to ensure you always will detect a state change.  If the INx pin voltage is not held at the new state for a time greater than the polling cycle, then there is a chance that the voltage has returned to the previous value when the pin is sampled, and the device will not detect the state change.

Regards,

Jonathan

Hi Roberto,

Unfortunately there is not a method to sample any input pin faster than 2ms.

The datasheet uses the term "polling" in a couple of ways and this can cause some confusion.  This is why I used the word "sample" in addition to the "polling cycle" in my previous response.

The "Polling Cycle" is the same for both "Continuous Mode" and "Polling Mode" and the fastest the device can "sample" or "poll" the inputs is defined by the t_{POLL_TIME} parameter which is configurable in the POLL_TIME field of the CONFIG Register to be between 2ms and 4096ms.

The difference between the "Continuous Mode" and the "Polling Mode" is what the device does with the wetting current during the "Polling Cycle".

Because the wetting current is only needed to create the voltage during the 18-24us window of time when the input pin is "sampled', the wetting current can be disabled after the sample measurement is complete to save power.  This mode of operation is called "Polling Mode" and the device will enable the wetting current for a period of time defined by the POLL_ACT_TIME field of the CONFIG register.  The capacitance on the input pin will need some time to charge and stabilize the voltage before the input pin is sampled which occurs during the last 18-24us of the POLL_ACT_TIME.  But once the pin has been sampled, the wetting current is disabled until the beginning of the next Polling Cycle where all the inputs are enabled again and the process repeats.

In Continuous Mode, the device keeps the wetting current enabled for the entire polling cycle.  It does not disable the wetting current after the input pin has been sample.  In this mode the POLL_ACT_TIME register is irrelevant and the input pins will simply be sampled once each polling cycle.

Regards,

Jonathan