C8051F120DK Silicon Laboratories Inc, C8051F120DK Datasheet - Page 192

• Manufacturer Part Number: C8051F120DK
• Description: DEVKIT-F120/21/22/23/24/25/26/27
• Manufacturer: Silicon Laboratories Inc
• Type: MCUr

Specifications of C8051F120DK

• Contents: Evaluation Board, Power Supply, USB Cables, Adapter and Documentation
• Processor To Be Evaluated: C8051F12x and C8051F13x
• Interface Type: USB
• Silicon Manufacturer: Silicon Labs
• Core Architecture: 8051
• Silicon Core Number: C8051F120
• Silicon Family Name: C8051F12x
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• For Use With/related Products: C8051F120, 121, 122, 123, 124, 125, 126, 127
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 336-1224

C8051F120/1/2/3/4/5/6/7
C8051F130/1/2/3
14.7.3. Powering on and Initializing the PLL
To set up and use the PLL as the system clock after power-up of the device, the following procedure
should be implemented:
If the PLL characteristics need to be changed when the PLL is already running, the following procedure
should be implemented:
192
Step 1. Ensure that the reference clock to be used (internal or external) is running and stable.
Step 2. Set the PLLSRC bit (PLL0CN.2) to select the desired clock source for the PLL.
Step 3. Program the Flash read timing bits, FLRT (FLSCL.5–4) to the appropriate value for the
Step 4. Enable power to the PLL by setting PLLPWR (PLL0CN.0) to ‘1’.
Step 5. Program the PLL0DIV register to produce the divided reference frequency to the PLL.
Step 6. Program the PLLLP3–0 bits (PLL0FLT.3–0) to the appropriate range for the divided
Step 7. Program the PLLICO1–0 bits (PLL0FLT.5–4) to the appropriate range for the PLL output
Step 8. Program the PLL0MUL register to the desired clock multiplication factor.
Step 9. Wait at least 5 µs, to provide a fast frequency lock.
Step 10. Enable the PLL by setting PLLEN (PLL0CN.1) to ‘1’.
Step 11. Poll PLLLCK (PLL0CN.4) until it changes from ‘0’ to ‘1’.
Step 12. Switch the System Clock source to the PLL using the CLKSEL register.
Step 1. The system clock should first be switched to either the internal oscillator or an external
Step 2. Ensure that the reference clock to be used for the new PLL setting (internal or external) is
Step 3. Set the PLLSRC bit (PLL0CN.2) to select the new clock source for the PLL.
Step 4. If moving to a faster frequency, program the Flash read timing bits, FLRT (FLSCL.5–4) to
Step 5. Disable the PLL by setting PLLEN (PLL0CN.1) to ‘0’.
Step 6. Program the PLL0DIV register to produce the divided reference frequency to the PLL.
Step 7. Program the PLLLP3–0 bits (PLL0FLT.3–0) to the appropriate range for the divided
Step 8. Program the PLLICO1-0 bits (PLL0FLT.5–4) to the appropriate range for the PLL output
Step 9. Program the PLL0MUL register to the desired clock multiplication factor.
Step 10. Enable the PLL by setting PLLEN (PLL0CN.1) to ‘1’.
Step 11. Poll PLLLCK (PLL0CN.4) until it changes from ‘0’ to ‘1’.
Step 12. Switch the System Clock source to the PLL using the CLKSEL register.
Step 13. If moving to a slower frequency, program the Flash read timing bits, FLRT (FLSCL.5–4)
clock source that is running and stable, using the CLKSEL register.
new clock rate (see
reference frequency.
frequency.
running and stable.
the appropriate value for the new clock rate (see
page 199
reference frequency.
frequency.
to the appropriate value for the new clock rate (see
).
PLL Frequency
Section “15. Flash Memory” on page 199
=
Reference Frequency
Rev. 1.4
Section “15. Flash Memory” on

Section “15. Flash Memory” on
-------------- -
PLLM
PLLN
).