C8051F360/1/2/3/4/5/6/7/8/9
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
SFR Page:
F
SFR Address: 0xAD
R/W
R
R/W
R/W
R/W
R/W
R/W
R/W
Reset Value
OSCLEN OSCLRDY OSCLF3 OSCLF2 OSCLF1 OSCLF0 OSCLD1 OSCLD0 00vvvv00
Bit7
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
Bit0
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.
Table 16.2. Internal Low Frequency Oscillator Electrical Characteristics
–40°C to +85°C unless otherwise specified.
Parameter
Oscillator Frequency
Conditions
OSCLD = 11b
Min
72
Typ
80
Max
88
Units
kHz
25 °C, V = 3.0 V,
DD
Oscillator Supply Current (from V
)
—
5.5
10
µA
DD
OSCLCN.7 = 1
Power Supply Sensitivity
Temperature Sensitivity
Constant Temperature
Constant Supply
—
—
2.4
30
—
—
%/V
ppm/°C
172
Rev. 1.0
SILICON [ SILICON ]
