1.3.2.4.1.4 PLL2 Registers
In addition to the main PLL that clocks the CPU, a second PLL (PLL2) exists for clocking the USB and HRCAP
modules.
shows the possible input and output configurations for PLL2.
DEVICECNF.SYSCLK2DIV2DIS
PLL2CTL.PLL2EN
PLL2CTL.PLL2CLKSRCSEL
INTOSC1
X1
XCLKIN
PLL2
PLL2CLK
HRCAP
/2
SYSCLK2 to
USB
0
1
Figure 1-28. PLL2 Input and Output Configurations
1.3.2.4.1.4.1 PLL2 Configuration (PLL2CTL) Register
Note
PLL2CTL is affected by the XRS signal only.
Figure 1-29. PLL2 Configuration (PLL2CTL) Register
15
3
2
1
0
Reserved
PLL2EN
PLL2CLKSRCSEL
R-0
R/W-1
R/W-00
LEGEND: R/W = Read/Write; R = Read only; -
n
= value after reset
Table 1-27. PLL2 Configuration (PLL2CTL) Register Field Descriptions
Bit
Field
Value
15-3
Reserved
Any writes to these bits must always have a value of 0.
2
PLL2EN
PLL enabled or disabled: This bit decides if PLL2 is enabled or not
0
PLL2 is powered off – clock to SYSCLK2 is a direct feed from input clock source as decided by the
PLL2CLKSRCSEL bit
1
PLL2 is enabled and clock to SYSCLK2 will depend on the DEVICECNF[SYSCLK2DIV2DIS] bit.
1-0
PLL2CLKSRCSEL
PLL2 Clock Source Select Bits: These bit select the source for the PLL2 input clock:
00
Internal oscillator 1 is selected as clock to PLL2
01
Internal oscillator 1 is selected as clock to PLL2
10
X1 clock source is selected as clock to PLL2
11
GPIO_XCLKIN is selected as clock to PLL2
On XRS low and after XRS goes high, X1 is selected as clock source to the USB PLL by default.
The user would need to select X1 or GPIO_XCLKIN as clock source during their initialization
process.
Whenever the user changes the clock source using these bits, the
DEVICECNF[SYSCLK2DIV2DIS] bit will be automatically forced to zero. This prevents potential
PLL overshoot. The user will then have to write to the DEVICECNF[SYSCLK2DIV2DIS] bit to
configure the appropriate divisor ratio.
(1)
This register is EALLOW protected. See
for more information.
System Control and Interrupts
82
TMS320x2806x Microcontrollers
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
Copyright © 2022 Texas Instruments Incorporated
Содержание TMS320 2806 Series
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