PRCM
CLK_32KHZ
From PRCM
0
1
Device
To WDT1
PRCM.CLKSEL_WDT1_
CLK.CLKSEL
(Default: 0)
On-Chip
32K RC Osc
(CLK_RC32K)
~32 kHz
32 kHz
To DMTIMER0
CLKOUT2
CLKOUT1
2
0
1
3
4
Master
Osc
(CLK_M_OSC)
32K Osc
(CLK_32K_RTC)
PRCM
1/1(0)
1/2(1)
1/3(2)
1/4(3)
1/5(4)
1/6(5)
1/7(6)
L3F_CLK
DDR_PHY_CLK
PER_CLKOUT_M2
PIXEL_CLK
PRCM.CM_CLKOUT_CTRL.CLKOUT2SOURCE
(Default = 0)
PRCM.CM_CLKOUT_CTRL.CLKOUT2DIV
(Default = 0)
Power, Reset, and Clock Management
Note: M2 divider can also be changed on-the-fly (i.e., there is no need to put the PLL in bypass and back
to lock mode). After changing CM_DIV_M2_DPLL_DDR.DPLL_CLKOUT_DIV, check
CM_DIV_M2_DPLL_DDR.DPLL_CLKOUT_DIVCHACK for a toggle (a change from 0 to 1 or 1 to 0) to see
if the change was acknowledged by the PLL.
8.1.6.12 CLKOUT Signals
The CLKOUT1 and CLKOUT2 signals go device pads and should mainly be used as debug testpoints.
Using these signals for time-critical external circuits is discouraged because of unpredictable jitter
performance. For more information, see the device datasheet, AM335x ARM Cortex-A8 Microprocessors
(MPUs) (literature number
). CLKOUT1 is created from the master oscillator. CLKOUT2 can be
sourced from the 32-KHz crystal oscillator or any of the PLL (except MPU PLL) outputs. The selected
output can be further modified by a programmable divider to create the desired output frequency.
Figure 8-15. CLKOUT Signals
8.1.6.13 Timer Clock Structure
The CLK_32KHZ clock is an accurate 32.768-MHz clock derived from the PER PLL and can also be
selected for the WDT1. The DMTIMER0 can only be clocked from the internal RC oscillator
(CLK_RC32K). The clock options are shown in
Figure 8-16. Watchdog Timer Clock Selection
All mux selections are in PRCM unless explicitly shown otherwise in the diagrams.
533
SPRUH73H – October 2011 – Revised April 2013
Power, Reset, and Clock Management (PRCM)
Copyright © 2011–2013, Texas Instruments Incorporated