Embedded Systems Questions and Answers – Timer

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This set of Embedded Systems Multiple Choice Questions & Answers (MCQs) focuses on “Timer”.

1. Which of the following helps in the generation of waveforms?
a) timer
b) inputs
c) outputs
d) memory
View Answer

Answer: a
Explanation: The embedded systems have a timing component called timer or counter which helps in the timing reference for control sequence, provides system tick for the operating system and also helps in the generation of waveforms for the serial port baud rate generation.
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2. Which bit size determines the slowest frequency?
a) counter size
b) pre-scalar value
c) counter
d) timer
View Answer

Answer: b
Explanation: The pre-scalar value determines the slowest frequency that can be generated from a given clock input. Actually the bit size are determined by the pre-scalar value and the conuter size.

3. Which bit size determines the maximum value of the counter-derived period?
a) counter size
b) pre-scalar value
c) bit size
d) byte size
View Answer

Answer: a
Explanation: The bit size are basically determined by its fundamental properties, that is, the pre-scalar value and the counter size. The counter size determines the maximum value of the counter derived period.

4. Which of the following timer is suitable for IBM PC?
a) IA-32
b) Intel 8253
c) Intel 64
d) 8051 timer
View Answer

Answer: b
Explanation: The Intel 8253 timer is suitable for the IBM PC. IA-32 and Intel 64 are the offload timers used only for Intel. The 8051 timer is used for the timing program in 8051.

5. Which of the following is mode 0 in 8253?
a) interrupt on start count
b) interrupt for wait statement
c) interrupt on terminal count
d) no interrupt
View Answer

Answer: c
Explanation: The interrupt on the terminal count is known as mode 0 for the 8253. An initial value is loaded into the count register and then starts to count down at the frequency which is determined by the clock input. When the count reaches zero, an interrupt is generated.
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6. Which determines the mode 1 in the Intel 8253?
a) interrupt on terminal count
b) programmable one-shot
c) rate generator
d) square wave rate generator
View Answer

Answer: b
Explanation: Programmable one-shot is also known as mode 1 in the Intel 8253. In mode 1, a single pulse with a programmable duration is created first and then the pulse length is loaded into the counter and when the external gate signal is high, the rising edge starts the counter to count down to zero and the counter output signal goes high to start the external pulse. When the counter reaches to zero, the counter output goes low and thus the ending of the pulse.

7. Which mode of 8253 can provide pulse width modulation?
a) programmable one-shot
b) square wave rate generator
c) software triggered strobe
d) hardware triggered strobe
View Answer

Answer: a
Explanation: Mode 1 of the Intel 8253 can provide pulse width modulation for the power control where the gate is connected to a zero crossing detector or a clock source.

8. Which of the following is the mode 3 in the Intel timer 8253?
a) rate generator
b) hardware triggered strobe
c) square wave rate generator
d) software triggered strobe
View Answer

Answer: a
Explanation: The rate generator is the mode 3 in Intel 8253 timer. The square wave generator is the mode 4 and the hardware triggered strobe is the mode 5 in the Intel 8253 timer.

9. Which of the following determines the rate generation?
a) divide by N
b) multiply by N
c) addition by N
d) subtraction by N
View Answer

Answer: a
Explanation: The rate generator mode is determined by the mode 3 with the Intel 8253. It is a simple divide by N mode where N is the initial value loaded into the counter.
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10. Which mode of the Intel 8253 timer can generate a square wave?
a) mode 1
b) mode 2
c) mode 3
d) mode 4
View Answer

Answer: d
Explanation: The mode 4 is the square wave generator. This mode is similar to mode 3 except that the waveform is a square wave.

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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