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SPRS230M – OCTOBER 2003 – REVISED MARCH 2011
The PLL, clocking, watchdog and low-power modes, are controlled by the registers listed in
Table 3-15. PLL, Clocking, Watchdog, and Low-Power Mode Registers
(1)
NAME
XCLK
PLLSTS
Reserved
HISPCP
LOSPCP
PCLKCR0
PCLKCR1
LPMCR0
Reserved
PLLCR
SCSR
WDCNTR
Reserved
WDKEY
Reserved
WDCR
Reserved
(1)
ADDRESS
0x7010
0x7011
0x7012 – 0x7019
0x701A
0x701B
0x701C
0x701D
0x701E
0x701F – 0x7020
0x7021
0x7022
0x7023
0x7024
0x7025
0x7026 – 0x7028
0x7029
0x702A – 0x702F
SIZE (x16)
1
1
8
1
1
1
1
1
1
1
1
1
1
1
3
1
6
PLL Status Register
Reserved
High-Speed Peripheral Clock Prescaler Register (for HSPCLK)
Low-Speed Peripheral Clock Prescaler Register (for LSPCLK)
Peripheral Clock Control Register 0
Peripheral Clock Control Register 1
Low-Power Mode Control Register 0
Reserved
PLL Control Register
System Control and Status Register
Watchdog Counter Register
Reserved
Watchdog Reset Key Register
Reserved
Watchdog Control Register
Reserved
DESCRIPTION
XCLKOUT Pin Control, X1 and XCLKIN Status Register
All of the registers in this table are EALLOW protected.
3.6.1
OSC and PLL Block
shows the OSC and PLL block on the 280x.
OSCCLK
XOR
PLLSTS[OSCOFF]
PLL
OSCCLK
OSCCLK
or
VCOCLK
n
0
XCLKIN
(3.3-V Clock Input)
0
CLKIN
VCOCLK
n
/2
PLLSTS[PLLOFF]
X1
On-Chip
Oscillator
X2
4-bit PLL Select
(PLLCR)
PLLSTS[CLKINDIV]
Figure 3-10. OSC and PLL Block Diagram
The on-chip oscillator circuit enables a crystal/resonator to be attached to the 280x devices using the X1
and X2 pins. If the on-chip oscillator is not used, an external oscillator can be used in either one of the
following configurations:
1. A 3.3-V external oscillator can be directly connected to the XCLKIN pin. The X2 pin should be left
unconnected and the X1 pin tied low. The logic-high level in this case should not exceed V
DDIO
.
2. A 1.8-V external oscillator can be directly connected to the X1 pin. The X2 pin should be left
unconnected and the XCLKIN pin tied low. The logic-high level in this case should not exceed V
DD
.
Copyright © 2003–2011, Texas Instruments Incorporated
Functional Overview
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