C8051F410DK Silicon Laboratories Inc, C8051F410DK Datasheet - Page 182

• Manufacturer Part Number: C8051F410DK
• Description: KIT DEV FOR C8051F41X
• Manufacturer: Silicon Laboratories Inc
• Type: MCUr

Specifications of C8051F410DK

• Contents: Evaluation Board, Power Supply, USB Cables, Adapter and Documentation
• Processor To Be Evaluated: C8051F41x
• Interface Type: USB
• Silicon Manufacturer: Silicon Labs
• Core Architecture: 8051
• Silicon Core Number: C8051F410
• Silicon Family Name: C8051F41x
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• For Use With/related Products: Silicon Laboratories C8051F41x
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 336-1314

C8051F410/1/2/3
20.2. smaRTClock Clocking Sources
The smaRTClock peripheral is clocked from its own timebase, independent of SYSCLK. The RTCCLK
timebase is derived from the smaRTClock oscillator circuit. This oscillator has two modes of operation:
Crystal Mode, and Self-Oscillate Mode. The oscillation frequency is 32.768 kHz in Crystal Mode and can
be configured to roughly 20 kHz or 40 kHz in Self-Oscillate Mode. The frequency of the smaRTClock oscil-
lator can be measured with respect to another oscillator using Timer 2 or Timer 3. Section
“
Note: The smaRTClock clock can be selected as system clock and routed to a port pin. See SFR
Definition 19.5. “CLKSEL: Clock Select” on page 174 and Section “
20.2.1. Using the smaRTClock Oscillator in Crystal Mode
When using Crystal Mode, a 32.768 kHz crystal should be connected between XTAL3 and XTAL4. No
other external components are required. The following steps show how to start the smaRTClock crystal
oscillator in software:
20.2.2. Using the smaRTClock Oscillator in Self-Oscillate Mode
When using Self-Oscillate Mode, the XTAL3 and XTAL4 pins should be shorted together. The following
steps show how to configure smaRTClock for use in Self-Oscillate Mode:
182
24.2.3. External/smaRTClock Capture Mode
Note: Software should avoid read modify write instructions when writing values to RTC0DAT. 
Bits 7–0: RTC0DAT. smaRTClock Data Bits
R/W
Bit7
Step 1. Set smaRTClock to Crystal Mode (XMODE = 1).
Step 2. Optional. Enable Automatic Gain Control (AGCEN = 1).
Step 3. Optional. Enable smaRTClock Bias Doubling (BIASX2 = 1).
Step 4. Enable power to the smaRTClock oscillator circuit (RTC0EN = 1).
Step 5. Poll the smaRTClock Clock Valid Bit (CLKVLD) until the crystal oscillator stabilizes.
Step 6. Optional . Clear BIASX2 to ‘0’ after the oscillator stabilizes to conserve power.
Step 1. Set smaRTClock to Self-Oscillate Mode (XMODE = 0).
Step 2. Set the desired oscillation frequency: 
Step 3. The oscillator starts oscillating instantaneously.
Holds data transferred to/from the internal smaRTClock register selected by RTC0ADR.
For oscillation at about 20 kHz, set BIASX2 = 0. 
For oscillation at about 40 kHz, set BIASX2 = 1.
R/W
Bit6
SFR Definition 20.3. RTC0DAT: smaRTClock Data
R/W
Bit5
R/W
Bit4
” on page
Rev. 1.1
R/W
Bit3
241
shows how this can be accomplished.
R/W
Bit2
18. Port Input/Output
R/W
Bit1
SFR Address:
R/W
Bit0
” on page
0xAD
Reset Value
Variable
147
.