C8051F312 Silicon Laboratories Inc, C8051F312 Datasheet - Page 67

• Manufacturer Part Number: C8051F312
• Description: IC 8051 MCU 8K FLASH 32LQFP
• Manufacturer: Silicon Laboratories Inc
• Series: C8051F31xr

Specifications of C8051F312

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 25MHz
• Connectivity: SMBus (2-Wire/I²C), SPI, UART/USART
• Peripherals: POR, PWM, Temp Sensor, WDT
• Number Of I /o: 29
• Program Memory Size: 8KB (8K x 8)
• Program Memory Type: FLASH
• Ram Size: 1.25K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 3.6 V
• Data Converters: A/D 21x10b
• 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: -
• Other names: 336-1151

6.
The voltage reference MUX on C8051F310/1/2/3/6 devices is configurable to use an externally connected
voltage reference, or the power supply voltage (see Figure 6.1). The REFSL bit in the Reference Control
register (REF0CN) selects the reference source. For an external source, REFSL should be set to ‘0’; For
V
The BIASE bit enables the internal voltage bias generator, which is used by the ADC, Temperature Sensor,
and Internal Oscillator. This bit is forced to logic 1 when any of the aforementioned peripherals is enabled.
The bias generator may be enabled manually by writing a ‘1’ to the BIASE bit in register REF0CN; see
SFR Definition 6.1 for REF0CN register details. The electrical specifications for the voltage reference cir-
cuit are given in Table 6.1.
Important Note About the VREF Input: Port pin P0.0 is used as the external VREF input. When using an
external voltage reference, P0.0 should be configured as analog input and skipped by the Digital Crossbar.
To configure P0.0 as analog input, set to ‘0’ Bit0 in register P0MDIN. To configure the Crossbar to skip
P0.0, set to ‘1’ Bit0 in register P0SKIP. Refer to
plete Port I/O configuration details.
The temperature sensor connects to the highest order input of the ADC0 positive input multiplexer (see
Section “5.1. Analog Multiplexer” on page 51
enables/disables the temperature sensor. While disabled, the temperature sensor defaults to a high imped-
ance state and any ADC0 measurements performed on the sensor result in meaningless data.
DD
as the reference source, REFSL should be set to ‘1’.
GND
VDD
Voltage Reference (C8051F310/1/2/3/6 only)
R1
Reference
External
Voltage
Circuit
Figure 6.1. Voltage Reference Functional Block Diagram
VREF
VDD
REF0CN
0
1
Section “13. Port Input/Output” on page 129
Rev. 1.7
for details). The TEMPE bit in register REF0CN
IOSCEN
C8051F310/1/2/3/4/5/6/7
EN
EN
Bias Generator
Temp Sensor
To Analog Mux
Internal
VREF
(to ADC)
To ADC, Internal
Oscillator
for com-
67