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6.5.2.2
Pre-Divider (PREDIV), PLL Multiplier (PLLM), and Post-Divider (POSTDIV)
6.5.3 PLL Power Down and Wakeup
6.6
PLL Controller Register Map
6.6.1 Introduction
PLL Controller Register Map
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To change the values of PREDIV, PLLM, or POSTDIV; the PLL controller must first be placed in bypass
mode. Perform the following steps to modify PREDIV, PLLM, or POSTDIV ratios.
1. In PLLCTL, write PLLEN = 0 to place the PLL in bypass mode.
2. Wait at least 4 reference clock cycles for the PLLEN mux to change.
3. In PLLCTL, write PLLRST = 1 (assert PLL).
4. Modify PREDIV, PLLM, and/or POSTDIV ratios.
5. Wait at least 5 miro-seconds for the PLL reset.
6. In PLLCTL, write PLLRST = 0 (de-assert PLL reset)
7. Wait at least 8000 reference clock cycles for the PLL to lock.
8. In PLLCTL, write PLLEN = 1 (switch from bypass mode to PLL mode).
The PLL may be powered down, in which case the PLL controller is in bypass mode and the device runs
from input reference clock. The device is still able to run when the PLL is powered down because it is still
being clocked by the bypass clock.
Perform the following procedure to power down the PLL.
1. In PLLCTL, write PLLEN = 0 (bypass mode).
2. Wait at least 4 reference clock cycles for the PLLEN mux to change.
3. In PLLCTL, write PLLPWRDN = 1 to power down the PLL.
To wakeup the PLL from its power-down mode, follow the PLL sequence described in
.
lists the base address for the PLLC1 and PLLC2 registers.
lists the memory-mapped
registers for PLLC1 and PLLC2. Also, see the device memory map
for the base addresses of
these registers.
Table 6-3. PLL and Reset Controller Module Instance Table
Instance ID
Base Address
End Address
Size
PLLC1
0x1C4 0800
0x1C4 0BFF
0x 400
PLLC2
0x1C4 0C00
0x1C4 0FFF
0x 400
Table 6-4. PLLC Registers
Offset
Acronym
Register Description
Section
00h
PID
Contains peripheral ID and revision information
100h
PLLCTL
Controls PLL operations
110h
PLLM
PLL Multiplier Control
114h
PREDIV
Pre-divider control
118h
PLLDIV1
Divider 1 control-divider for SYSCLK1
11Ch
PLLDIV2
Divider 2 control-divider for SYSCLK2
120h
PLLDIV3
Divider 3 control-divider for SYSCLK3
128h
POSTDIV
Post-divider control
12Ch
BPDIV
Bypass divider control
44
PLL Controllers (PLLCs)
SPRUFX7 – July 2008