SM320F2808-EP Datasheet, PDF (38/118 Pages) Texas Instruments – Digital Signal Processors

SM320F2808-EP, SM320F2806-EP
SM320F2801-EP
Digital Signal Processors
SGLS316A – MARCH 2006 – REVISED FEBRUARY 2007
www.ti.com
The PLL, clocking, watchdog and low-power modes, are controlled by the registers listed in Table 3-13.
Table 3-13. 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
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
DESCRIPTION
XCLKOUT Pin Control, X1 and XCLKIN Status Register
PLL Status Register
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
PLL Control Register
System Control and Status Register
Watchdog Counter Register
Watchdog Reset Key Register
Watchdog Control Register
(1) All of the registers in this table are EALLOW protected.
3.6.1 OSC and PLL Block
Figure 3-8 shows the OSC and PLL block on the 280x.
XCLKIN
(3.3-V clock input)
OSCCLK
xor
PLLSTS[OSCOFF]
OSCCLK
PLL ^VCOCLK
0 _{OSCCLK or}
VCOCLK
n _n≠0
CLKIN
/2
X1
On chip
oscillator
X2
PLLSTS[PLLOFF]
PLLSTS[CLKINDIV]
4-bit PLL Select (PLLCR)
Figure 3-8. 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
38
Functional Overview
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