Question

The PORTB of an ATmega8 microcontroller is interfaced to 6 switches PB0-PB5. The PORTD.0 (PD0) is connected to a green LED (The green LED is ON when a logic 0 is output to PD0). What is the C instruction that checks whether PB5 is 1, and when it is, it turns the green LED OFF?

a. If (((PINB & (1<< 4)) != 0) PORTD ^= 0x01;
b. If (((PINB & 0x20) != 0) PORTD ^= 0x01;
c. If (((PINC & (1<<4)) != 0) PORTD &= 0x01;
d. If (((PINB|(1<<5)) != 0) PORTD |= 0x01;
e. If (((PINB |(1<<5)) != 0) PORTD &= 0xFE;

Answer 1

The correct C instruction that checks whether PB2 is 1 and turns the green LED off is option b.

Step-by-step explanation:

The correct C instruction that checks whether PB5 is 1 and turns the green LED off is option b. If (((PINB & 0x20) != 0) PORTD ^= 0x01.

Step-by-step explanation:

1. PINB is a register that represents the input value for PORTB. By performing the bitwise AND operation with 0x20 (binary 00100000), it checks the state of PB5. If the result is not equal to zero, it means that PB5 is 1.
2. PORTD ^= 0x01 is used to toggle the state of PD0. The XOR operation (^) with 0x01 (binary 00000001) inverts the least significant bit of PORTD, turning off the green LED.