C8051F320 Silicon Laboratories Inc, C8051F320 Datasheet - Page 118

• Manufacturer Part Number: C8051F320
• Description: IC 8051 MCU 16K FLASH 32LQFP
• Manufacturer: Silicon Laboratories Inc
• Series: C8051F32xr

Specifications of C8051F320

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 25MHz
• Connectivity: SMBus (2-Wire/I²C), SPI, UART/USART, USB
• Peripherals: Brown-out Detect/Reset, POR, PWM, Temp Sensor, WDT
• Number Of I /o: 25
• Program Memory Size: 16KB (16K x 8)
• Program Memory Type: FLASH
• Ram Size: 2.25K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 3.6 V
• Data Converters: A/D 17x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 32-LQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -

C8051F320/1
On C8051F320/1 devices, OSCICL is factory calibrated to obtain a 12 MHz base frequency (f
details oscillator programming for C8051F320/1 devices. Electrical specifications for the precision internal oscillator
are given in Table 13.3 on page 126. Note that the system clock may be derived from the programmed internal oscil-
lator divided by 1, 2, 4, or 8, as defined by the IFCN bits in register OSCICN. The divide value defaults to 8 follow-
ing a reset.
13.1.1. Programming the Internal Oscillator on C8051F320/1 Devices
The OSCICL reset value is factory calibrated to result in a 12 MHz internal oscillator with a ±1.5% accuracy; this fre-
quency is suitable for use as the USB clock (see
oscillator as described below.
Important Note: Once the internal oscillator frequency has been modified, the internal oscillator may not be used as
the USB clock as described in
brated frequency following any device reset, at which point the oscillator is suitable for use as the USB clock.
Software should read and adjust the value of OSCICL according to Equation 13.1 to obtain the desired frequency.
The example below shows how to obtain an 11.6 MHz internal oscillator frequency.
Important Note: If the sum of the reset value of OSCICL and ∆OSCICL is greater than 31 or less than 0, then the
device will not be capable of producing the desired frequency.
13.1.2. Internal Oscillator Suspend Mode
The internal oscillator may be placed in Suspend mode by writing ‘1’ to the SUSPEND bit in register OSCICN. In
Suspend mode, the internal oscillator is stopped until a non-idle USB event is detected
matches the polarity selected by the VBPOL bit in register REG0CN
must be enabled for a USB event to be detected.
118
f
f
The required change in period (∆T
Using Equation 13.1 and the above calculations, find ∆OSCICL:
∆OSCICL is rounded to the nearest integer (14) and added to the reset value of register OSCICL.
T
BASE
DES
∆OSCICL
f
∆T
2.87 10
BASE
BASE
is the desired internal oscillator frequency; T
DES
is the internal oscillator reset frequency; T
×
=
=
=
12000000Hz
----------------------- - s
12000000
9 –
----------------------- -
11600000
=
=
1
13.79
1
0.0025
–
×
----------------------- -
12000000
Section
------------ -
f
BASE
1
DES
1
) is the difference between the base period and the desired period.
×
13.4. The internal oscillator frequency will reset to its original factory-cali-
∆OSCICL
=
2.87
BASE
Section
DES
×
Rev. 1.1
is the reset oscillator period.
is the desired oscillator period.
10
T
f
DES
DES
9 –
13.4). Software may modify the frequency of the internal
s
=
=
11600000Hz
----------------------- - s
11600000
(Section
1
8.2). Note that the USB transceiver
(Section
BASE
).
Section 13.1.1
15) or VBUS