Which of the following interrupt is enabled when the contents of the SFR register is 7Fh?*1 pointA) ET1B) ET0C) EX1D) None of the above

The answer is B) ET0.

Here's the step-by-step explanation:

The SFR (Special Function Register) in question is the IE (Interrupt Enable) register in 8051 microcontroller. The IE register is responsible for enabling and disabling specific interrupts. The bits of the IE register are as follows:

• Bit 7 = EA (Global interrupt enable/disable)
• Bit 6 = - (Undefined, reserved)
• Bit 5 = ET2 (Timer 2 interrupt enable/disable)
• Bit 4 = ES (Serial port interrupt enable/disable)
• Bit 3 = ET1 (Timer 1 interrupt enable/disable)
• Bit 2 = EX1 (External interrupt 1 enable/disable)
• Bit 1 = ET0 (Timer 0 interrupt enable/disable)
• Bit 0 = EX0 (External interrupt 0 enable/disable)

When the contents of the SFR register is 7Fh (0111 1111 in binary), it means that all interrupts are enabled except the global interrupt (EA). So, ET1, ET0, EX1, and EX0 are all enabled. Therefore, the answer is not D) None of the above.

Among the options given, ET0 is enabled, so the answer is B) ET0.