Embedded System Timer MCQ Quiz – Objective Question with Answer for Embedded System Timer

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.

The pre-scaler value determines the lowest frequency that can be generated from a given clock input. Actually, the bit size is determined by the pre-scalar value and the counter size.

The bit size is 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.

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 timers are used for the timing program in 8051.

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.

The 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 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 zero, the counter output goes low and thus the ending of the pulse.

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.

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

The rate generator mode is determined by mode 3 with the Intel 8253. It is a simple divide by N mode where N is the initial value loaded into the counter.

Mode 4 is the square wave generator. This mode is similar to mode 3 except that the waveform is a square wave.