Analog tamper detection

Note This feature is only available for MCA firmware v1.0 and higher. To update your device, see MCA management application.

In an analog tamper interface, the event is triggered by the change on the analog comparator output. This output depends on the thresholds configured and the analog value of IO_IN pin. If the value is between the low and high thresholds (inside the window), the comparator output is high. In the other case, the comparator output is low. In other words, if the tamper input has been configured as active high, the event is signaled when the input is inside the window; if it was configured as active low, the event is triggered when the input is outside the window.

The voltage reference for the comparator can be configured to use either:

MCA_VCC: this is an input voltage for the ConnectCore 6UL module. For the ConnectCore 6UL SBC Pro and ConnectCore 6UL SBC Express reference designs, it is 3.0 V.
Internal voltage reference: this requires an external 100 nF capacitor to be connected in MCA_IO2/VREF line, and also it implies that that line will have 1.2 V output enabled (see 1.2 V Voltage reference section). Finally, all MCA ADCs and analog comparators will be forced to use this internal voltage reference.

CAUTION! The internal voltage reference is only available if LGA pads are accessible. Therefore the internal voltage reference does not work in the ConnectCore 6UL SBC Express since the capacitor cannot be connected.

Another important difference in analog tamper detection is that the input is sampled every 10 MCA-ticks (1 MCA-tick = 1/1024 second or 0,9765625 millisecond) in run mode and every configurable period in sleep/power-off (--ticks parameter).

Note Configuring the --ticks parameter affects power consumption in low-power mode.

Once the tamper event is triggered, the actions that take place are exactly the same as in the digital tamper detection interfaces. The following diagram shows the sequence of events: