Introduction
131
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
Phase-Locked Loop Controller (PLLC)
7.1
Introduction
This device has two phase-locked loop (PLL) controllers, PLLC0 and PLLC1. These PLL controllers
provide clock signals to most of the components of the device through various clock dividers.
Both PLL0 and PLL1 provide the following:
•
Glitch-free transitions when clock settings are changed
•
Domain clock alignment
•
Clock gating
•
PLL power-down
The clock outputs generated by the PLL controllers are:
•
Domain clocks: PLL0_SYSCLK[1-7] and PLL1_SYSCLK[1-3]
•
Auxiliary clock (PLL0_AUXCLK) from the PLLC0 reference clock source
Dividers that can be used for the PLL controllers are:
•
Pre-PLL divider: PREDIV
•
Post-PLL divider: POSTDIV
•
SYSCLK divider: D1, …, Dn
Various other control signals supported are:
•
PLL multiplier: PLLM
•
Software-programmable PLL bypass: PLLEN
7.2
PLL Controllers
PLL0 and PLL1 share the same internal architecture so they also share the same approach for mode
configuration.
PLL0 provides the primary system clock to the device. PLL0 operations are software programmable
through the PLL controller 0 (PLLC0) registers.
PLL1 provides the reference clocks to various peripherals (including DDR2/mDDR) and may generate
clocks that are asynchronous to the PLL0 clocks. PLL1 operations are software programmable through the
PLL controller 1 (PLLC1) registers.
shows the PLLC0 and PLLC1 architecture.
The PLL0 and PLL1 multipliers are controlled by their respective PLL multiplier control register (PLLM).
The PLLM defaults to a multiplier value of 13h at power-up, which results in a PLL multiplier of 20×. The
PLL0 and PLL1 output clocks may be divided-down for slower device operation using the PLL post-divider
control register (POSTDIV). The POSTDIV has a default value of /2, but may be modified through
software (using the RATIO field in POSTDIV) to achieve lower device operation frequencies. The default
PLLM and POSTDIV settings produce a 300-MHz PLL output clock when given a 30-MHz clock source.
At power-up, PLL0 and PLL1 are powered-down/disabled and must be powered-up by software through
the PLLPWRDN bit in their respective PLL control register (PLLCTL). Before each PLL completes the
power-up and frequency-lock sequence, the system operates in bypass mode by default and the system
clock (OSCIN) is provided directly from an input reference clock (square wave or internal oscillator)
selected by the CLKMODE bit in PLLCTL. After the power-up and frequency-lock sequences are
complete, software can switch the device to PLL mode operation (set the PLLEN bit in PLLCTL to 1).
The PLL controller registers are listed in