cannot understand analog compare interrupt [arduino micro]

I’m trying to make an analog comparasion interrupt (needs to be interrupt!) with ntc-resistor or ldr-resistor into the arduino micro and i cannot understand that how to make it right. There is no AIN1 pin on the pin description image of arduino micro !

I made the connection work somehow with the pin 6 and the limit seems to be between 0,4volts and 1,9 volts when the interruption is triggered. If i change the wire to pin 7 it still works ! ?

Some document showd that the AIN1 would the pin RX (no number)
So IF the ain1 pin is same as RX pin how can i change comparasion interrupt from it to for example to pin 7 ? I also need the rx and tx pins for accelerometer module so they cannot be reserved to ldr-interrupt!

ACSR =
    (0 << ACD) |    // Analog Comparator: Enabled
    (0 << ACBG) |   // Analog Comparator Bandgap Select: AIN0 is applied to the positive input
    (0 << ACO) |    // Analog Comparator Output: Off
    (1 << ACI) |    // Analog Comparator Interrupt Flag: Clear Pending Interrupt
    (1 << ACIE) |   // Analog Comparator Interrupt: Enabled
    (0 << ACIC) |   // Analog Comparator Input Capture: Disabled
    (0 << ACIS1) | (0 << ACIS0);   // Analog Comparator Interrupt Mode: Comparator Interrupt on Rising Output Edge

The Arduino Micro schematic shows that the RXD1/AIN1/INT2 pin (PORTD bit 2) is the Arduino D0/RX pin.

While the schematic shows

the RXD1/AIN1/INT2 pin (PORTD bit 2) is the Arduino D0/RX pin.

In reality the ATmega16/32U4 does not have an AIN1 pin. You can however select to compare against the analog input pins.