C8051F066-GQ Silicon Laboratories Inc, C8051F066-GQ Datasheet - Page 175

• Manufacturer Part Number: C8051F066-GQ
• Description: MCU 8-Bit C8051F06x 8051 CISC 32KB Flash 3.3V 100-Pin TQFP
• Manufacturer: Silicon Laboratories Inc
• Series: C8051F06xr

Specifications of C8051F066-GQ

• Package: 100TQFP
• Device Core: 8051
• Family Name: C8051F06x
• Maximum Speed: 25 MHz
• Operating Supply Voltage: 3.3 V
• Data Bus Width: 8 Bit
• Number Of Programmable I/os: 59
• Interface Type: I2C/SMBus/SPI/UART
• On-chip Adc: 2-chx16-bit
• Number Of Timers: 5
• Ram Size: 4.25 KB
• Program Memory Size: 32 KB
• Program Memory Type: Flash
• Operating Temperature: -40 to 85 °C
• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 25MHz
• Connectivity: EBI/EMI, SMBus (2-Wire/I²C), SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 59
• Voltage - Supply (vcc/vdd): 2.7 V ~ 3.6 V
• Data Converters: A/D 2x16b
• Oscillator Type: Internal
• Package / Case: 100-TQFP, 100-VQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 336-1221

15.4. External Crystal Example
If a crystal or ceramic resonator is used as an external oscillator source for the MCU, the circuit should be
configured as shown in Figure 15.1, Option 1. The External Oscillator Frequency Control value (XFCN)
should be chosen from the Crystal column of the table in Figure 15.5 (OSCXCN register). For example, an
11.0592 MHz crystal requires an XFCN setting of 111b.
When the crystal oscillator is enabled, the oscillator amplitude detection circuit requires a settle time to
achieve proper bias. Introducing a blanking interval of at least 1 ms between enabling the oscillator and
checking the XTLVLD bit will prevent a premature switch to the external oscillator as the system clock.
Switching to the external oscillator before the crystal oscillator has stabilized can result in unpredictable
behavior. The recommended procedure is:
Important Note on External Crystals: Crystal oscillator circuits are quite sensitive to PCB layout and
external noise. The crystal should be placed as close as possible to the XTAL pins on the device. The
traces should be as short as possible and shielded with ground plane from any other traces which could
introduce noise or interference. Crystal loading capacitors should be referenced to AGND.
15.5. External RC Example
If an RC network is used as an external oscillator source for the MCU, the circuit should be configured as
shown in Figure 15.1, Option 2. The capacitor should be no greater than 100 pF; however for very small
capacitors, the total capacitance may be dominated by parasitic capacitance in the PCB layout. To deter-
mine the required External Oscillator Frequency Control value (XFCN) in the OSCXCN Register, first
select the RC network value to produce the desired frequency of oscillation. If the frequency desired is
100 kHz, let R = 246 k and C = 50 pF:
f = 1.23( 10
Referring to the table in Figure 15.5, the required XFCN setting is 010.
15.6. External Capacitor Example
If a capacitor is used as an external oscillator for the MCU, the circuit should be configured as shown in
Figure 15.1, Option 3. The capacitor should be no greater than 100 pF; however for very small capacitors,
the total capacitance may be dominated by parasitic capacitance in the PCB layout. To determine the
required External Oscillator Frequency Control value (XFCN) in the OSCXCN Register, select the capaci-
tor to be used and find the frequency of oscillation from the equations below. Assume VDD = 3.0 V and C
= 50 pF:
f = KF / ( C * VDD ) = KF / ( 50 * 3 )
f = KF / 150
If a frequency of roughly 50 kHz is desired, select the K Factor from the table in Figure 15.5 as KF = 7.7:
f = 7.7 / 150 = 0.051 MHz, or 51 kHz
Therefore, the XFCN value to use in this example is 010.
Step 1. Enable the external oscillator.
Step 2. Wait at least1 ms.
Step 3. Poll for XTLVLD => ‘1’.
Step 4. Switch the system clock to the external oscillator.
3
) / RC = 1.23 ( 10
3
) / [ 246 * 50 ] = 0.1 MHz = 100 kHz
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