C8051F360 datasheet(172/288 Pages) SILABS

172 / 288 page

C8051F360/1/2/3/4/5/6/7/8/9

172

Rev. 1.0

16.2.1. Calibrating the Internal L-F Oscillator

Timers 2 and 3 include capture functions that can be used to capture the oscillator frequency, when run-

ning from a known time base. When either Timer 2 or Timer 3 is configured for L-F Oscillator Capture

Mode, a falling edge (Timer 2) or rising edge (Timer 3) of the low-frequency oscillator’s output will cause a

capture event on the corresponding timer. As a capture event occurs, the current timer value

(TMRnH:TMRnL) is copied into the timer reload registers (TMRnRLH:TMRnRLL). By recording the differ-

ence between two successive timer capture values, the low-frequency oscillator’s period can be calcu-

lated. The OSCLF bits can then be adjusted to produce the desired oscillator frequency.

SFR Definition 16.3. OSCLCN: Internal L-F Oscillator Control

Bit 7:

OSCLEN: Internal L-F Oscillator Enable.

0: Internal L-F Oscillator Disabled.

1: Internal L-F Oscillator Enabled.

Bit 6:

OSCLRDY: Internal L-F Oscillator Ready.

0: Internal L-F Oscillator frequency not stabilized.

1: Internal L-F Oscillator frequency stabilized.

Bits 5–2: OSCLF[3:0]: Internal L-F Oscillator Frequency Control bits.

Fine-tune control bits for the Internal L-F oscillator frequency. When set to 0000b, the L-F

oscillator operates at its fastest setting. When set to 1111b, the L-F oscillator operates at its

slowest setting.

Bits 1–0: OSCLD[1:0]: Internal L-F Oscillator Divider Select.

00: Divide by 8 selected.

01: Divide by 4 selected.

10: Divide by 2 selected.

11: Divide by 1 selected.

SFR Page:

SFR Address:

0xAD

R/W

Reset Value

OSCLEN OSCLRDY OSCLF3

OSCLF2

OSCLF1

OSCLF0 OSCLD1 OSCLD0 00vvvv00

Bit7

Bit6

Bit5

Bit4

Bit3

Bit2

Bit1

Bit0

Table 16.2. Internal Low Frequency Oscillator Electrical Characteristics

–40°C to +85°C unless otherwise specified.

Parameter

Conditions

Min

Typ

Max

Units

Oscillator Frequency

OSCLD = 11b

kHz

Oscillator Supply Current (from VDD)

25 °C, VDD = 3.0 V,

OSCLCN.7 = 1

—5.5

µA

Power Supply Sensitivity

Constant Temperature

—

2.4

—

%/V

Temperature Sensitivity

Constant Supply

—

ppm/°C

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