Microprocessors Questions and Answers – Power Control Register

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This set of Microprocessor Multiple Choice Questions & Answers (MCQs) focuses on “Power Control Register”.

1. The power control register is
a) used for power saving during idle state
b) used for eventual power off to 8051 chip
c) non-bit addressable register
d) all of the mentioned
View Answer

Answer: d
Explanation: The power control register is used for power saving during idle state of the microcontroller and eventual power off to the microcontroller chip. It has SMOD bit which is used to double the baud rate.
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2. The state of signals in idle mode is
a) ALE is high
b) PSEN is high
c) PSEN(active low) is high
d) ALE and PSEN(active low) are high
View Answer

Answer: d
Explanation: ALE and PSEN(active low) remain high in Idle mode.

3. To come out of idle mode, the external interrupt that is enabled is
a) SI(serial)
b) INT0
c) INT1
d) All of the mentioned
View Answer

Answer: d
Explanation: To come out of idle mode, any external interrupt that is enabled like SI(Serial), INT0 and INT1.

4. The microcontroller enters into power down mode when
a) SMOD bit of PCON is set
b) GF1 bit of PCON is set
c) PD bit of PCON is set
d) GF2 bit of PCON is set
View Answer

Answer: c
Explanation: If the PD bit of PCON register is set, it enters power down mode.

5. The clock signal is disabled to all parts of 8051 in
a) normal mode
b) idle mode
c) power down mode
d) addressing mode
View Answer

Answer: c
Explanation: In power down mode, the clock signal to all parts of 8051 chip is disabled.
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6. During power down to save battery, the supply voltage can be reduced to a value of
a) 4 volts
b) 2 volts
c) 8 volts
d) 1 volt
View Answer

Answer: b
Explanation: The supply voltage can be reduced to a value of around 2 volts, during power down to save battery.

7. The signal that only pulls the microcontroller(8051) out of the power down mode is
a) CLEAR
b) LEAVE
c) RESET
d) EXIT
View Answer

Answer: c
Explanation: Only Reset signal can pull 8051 out of the power down mode.

8. The state of signals in power down mode is
a) ALE is high
b) PSEN is low
c) ALE and PSEN(active low) are high
d) ALE and PSEN(active low) are low
View Answer

Answer: d
Explanation: ALE and PSEN(active low) remain low in power down mode of 8051.

9. In power down mode,
a) Port pins maintain their logic levels
b) SFRs maintain their logic levels
c) Clock signal is disabled
d) All of the mentioned
View Answer

Answer: d
Explanation: In power down mode, the clock signal is disabled and all the port pins and respective SFRs maintain their logic levels.

10. The SMOD bit is used to
a) decrease the baud rate by 2
b) increase the baud rate by 4
c) increase the baud rate by 2
d) triple the baud rate
View Answer

Answer: c
Explanation: The SMOD bit is used to double the baud rate.
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Sanfoundry Global Education & Learning Series – Microprocessors.

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To practice all areas of Microprocessors, here is complete set of 1000+ Multiple Choice Questions and Answers.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn