SPRUJ17H March 2022 – October 2024 AM2631 , AM2631-Q1 , AM2632 , AM2632-Q1 , AM2634 , AM2634-Q1
ROM code must be aware of the reference clock provided to PLLs. That is, the speed of the quartz crystal, or the clock supplied by an external clock oscillator.
The Public ROM code configures PLLs which are required during boot. ROM configures only core PLL during boot. The ROM Core PLL configuration details is as follows:
InputClockDiv (N) = 0xB
Multiplier (M) = 0x180
Divider (N2) = 0x1
Post-Divider (M2) = 0X1
Fractional Multiplier (Frac) = 0x0
Using the above values, the PLL output frequency is computed as follows:
XTAL_IN/(N + 1) = 25/12 = 2.0833 MHz
(XTAL_IN * M) /(N + 1) = 2.08333 * 384 = 800MHz
(XTAL_IN * M) /[(N2 +1) * (N + 1)] = 800 / 2 = 400MHz
400/ M2 = 400MHz
See ADPLLLJ Module section in the Clocking section of Device configuration chapter for more details on PLL configuration sequence and the PLL output frequency equation.
Where, XTAL_IN is the XTAL Clock source frequency (25MHz)
This Core PLL output (ADPLL0) is used to configure R5 clock = 400MHz and SysClk = 200MHz