SPRUIZ1B July 2023 – August 2024 TMS320F28P650DH , TMS320F28P650DK , TMS320F28P650SH , TMS320F28P650SK , TMS320F28P659DH-Q1 , TMS320F28P659DK-Q1 , TMS320F28P659SH-Q1
The PLL/AUXPLL is responsible for synthesizing an output frequency from the input clock (from the oscillator). Figure 3-10 shows a simple block diagram of the PLL/AUXPLL. The PLL/AUXPLL divides the reference input for a lower frequency input into the PLL/AUXPLL by (REFDIV + 1). Then multiplies this internal frequency by IMULT to get the VCO output clock. The PLL/AUXPLL output is divided by (ODIV + 1) to generate PLLRAWCLK/AUXPLLRAWCLK that is further divided by SYSCLKDIVSEL.PLLSYSCLKDIV/AUXCLKDIVSEL.AUXPLLDIV to generate PLLSYSCLK/AUXCLK.
There are two PLLs (SYSPLL and AUXPLL) and the equations shown in Figure 3-10 can be used to configure the respective PLL.
For the permissible values of the multipliers and dividers, see the documentation for the respective registers.
Many combinations of multiplier and divider can produce the same output frequency. However, the product of the reference clock frequency and the multiplier (known as the VCO frequency) must be in the range specified in the data manual.
The clock source and PLL configuration registers are shared between the two CPUs (CPU1 and CPU2). Register access is controlled by way of a semaphore, which is described in Chapter 15.