Datasheet

X2
X1/XCLKIN
On-Chip
Oscillator
(OSC)
PLL
Bypass
/2
XF_XPLLDIS
OSCCLK (PLL Disabled)
Latch
XPLLDIS
XRS
PLL
4-Bit PLL Select
SYSCLKOUT
1
0
CLKIN
CPU
4-Bit PLL Select
XCLKIN
PLL Block
TMS320F2810, TMS320F2811, TMS320F2812
TMS320C2810, TMS320C2811, TMS320C2812
SPRS174T –APRIL 2001–REVISED MAY 2012 www.ti.com
3.8 OSC and PLL Block
Figure 3-9 shows the OSC and PLL block on the F281x and C281x.
Figure 3-9. OSC and PLL Block
The on-chip oscillator circuit enables a crystal to be attached to the F281x and C281x devices using the
X1/XCLKIN and X2 pins. If a crystal is not used, then an external oscillator can be directly connected to
the X1/XCLKIN pin and the X2 pin is left unconnected. The logic-high level in this case should not
exceed V
DD
. The PLLCR bits [3:0] set the clocking ratio.
50 Functional Overview Copyright © 2001–2012, Texas Instruments Incorporated
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