C8051F018-GQR Silicon Laboratories Inc, C8051F018-GQR Datasheet - Page 84

• Manufacturer Part Number: C8051F018-GQR
• Description: IC 8051 MCU 16K FLASH 64TQFP
• Manufacturer: Silicon Laboratories Inc
• Series: C8051F018r

Specifications of C8051F018-GQR

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 25MHz
• Connectivity: SMBus (2-Wire/I²C), SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, Temp Sensor, WDT
• Number Of I /o: 32
• Program Memory Size: 16KB (16K x 8)
• Program Memory Type: FLASH
• Ram Size: 1.25K x 8
• Voltage - Supply (vcc/vdd): 2.8 V ~ 3.6 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 64-TQFP, 64-VQFP
• Processor Series: C8051F0x
• Core: 8051
• Data Bus Width: 8 bit
• Data Ram Size: 1.25 KB
• Interface Type: I2C, SMBus, SPI, UART
• Maximum Clock Frequency: 25 MHz
• Number Of Programmable I/os: 32
• Number Of Timers: 4 bit
• Operating Supply Voltage: 2.8 V to 3.6 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: PK51, CA51, A51, ULINK2
• Development Tools By Supplier: C8051F005DK
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 10 bit, 8 Channel
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Lead Free Status / Rohs Status: Details

12.1.
If a crystal or ceramic resonator were used to generate the system clock for the MCU, the circuit would be as shown
in Figure 12.1, Option 1. For an ECS-110.5-20-4 crystal, the resonate frequency is 11.0592MHz, the intrinsic
capacitance is 7pF, and the ESR is 60. The compensation capacitors should be 33pF each, and the PWB parasitic
capacitance is estimated to be 2pF. The appropriate External Oscillator Frequency Control value (XFCN) from the
Crystal column in the table in Figure 12.3 (OSCXCN Register) should be 111b.
Because the oscillator detect circuitry needs time to settle after the crystal oscillator is enabled, software should wait
at least 1ms between enabling the crystal oscillator and polling the XTLVLD bit. The recommend procedure is:
1. Enable the external oscillator
2. Wait at least 1 ms
3. Poll for XTLVLD '0' ==> '1'
4. Switch to the external oscillator
Switching to the external oscillator before the crystal oscillator has stabilized could result in unpredictable behavior.
NOTE: Crystal oscillator circuits are quite sensitive to PCB layout. The crystal should be placed as close as possible
to the XTAL pins on the device, keeping the traces as short as possible and shielded with ground plane from any
other traces which could introduce noise or interference.
12.2.
If an external RC network were used to generate the system clock for the MCU, the circuit would be as shown in
Figure 12.1, Option 2. The capacitor must be no greater than 100pF, but using a very small capacitor will increase
the frequency drift due to the PWB parasitic capacitance. To determine 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 100kHz, let R = 246k and C = 50pF:
12.3.
If an external capacitor were used to generate the system clock for the MCU, the circuit would be as shown in
Figure 12.1, Option 3. The capacitor must be no greater than 100pF, but using a very small capacitor will increase
the frequency inaccuracy due to the PWB parasitic capacitance. To determine the required External Oscillator
Frequency Control value (XFCN) in the OSCXCN Register, select the capacitor to be used and find the frequency
of oscillation from the equations below. Assume AV+ = 3.0V and C = 50pF:
If a frequency of roughly 90kHz is desired, select the K Factor from the table in Figure 12.3 as KF = 13:
Therefore, the XFCN value to use in this example is 011.
f = 1.23(10
XFCN  log
XFCN  log
XFCN  2, or code 010
f = KF / (C * VDD) = KF / (50 * 3)
f = KF / 150
f = 13 /150 = 0.087MHz, or 87kHz
External Crystal Example
External RC Example
External Capacitor Example
3
)/RC = 1.23(10
2
2
(f/25kHz)
(100kHz/25kHz) = log
3
) / [246 * 50] = 0.1MHz = 100kHz
2
(4)
Rev. 1.2
C8051F018
C8051F019
84