To calculate Fcy (Internal instruction cycle frequency), we need to determine the frequency division factor (N) of the phase-locked loop (PLL). The PLL is used to multiply the primary oscillator frequency to generate the desired internal instruction cycle frequency.
Given:
Primary oscillator frequency (Fosc) = 7.648 GHz
We can calculate Fcy as follows:
Fcy = (Fosc × N) / 4
To determine the frequency division factor (N), we need to know the desired Fcy value or the specific microcontroller being used. Assuming the desired Fcy value is not provided, we'll use the general formula for N:
N = Fcy_desired / Fosc
Typically, the desired Fcy value for a microcontroller is known (e.g., 30 MHz, 40MHz, etc.), but without that information, we can't determine the exact value of Fcy and Tcy.
However, I will provide an example calculation using a desired Fcy value of 40 MHz for illustrative purposes:
Desired Fcy = 40 MHz
Desired Fcy = 40,000,000 Hz
N = Desired Fcy / Fosc
N = 40,000,000 Hz / 7,648,000,000 Hz
N ≈ 5.219
Now, we can calculate Fcy using the obtained value of N:
Fcy = (Fosc × N) / 4
Fcy = (7,648,000,000 Hz × 5.219) / 4
Fcy ≈ 10,008,432.76 Hz
So, the approximate Fcy value is 10,008,432.76 Hz or 10.008 MHz.
To calculate Tcy (Internal instruction cycle time), we can use the reciprocal of Fcy:
Tcy = 1 / Fcy
Tcy = 1 / 10,008,432.76 Hz
Tcy ≈ 99.92 ns
Therefore, the approximate Tcy value is 99.92 ns.
Question 2.
The primary oscillator is used as the clock source and its frequency is 7.648 GHz. The PLL is used. In that case, what is Fcy (Internal instruction cycle frequency)? Also, what is Tcy? You must show your calculation. Failing to do so will result zero mark for this question.
1 answer
1 answer