C8051F131R Silicon Labs, C8051F131R Datasheet - Page 240

• Manufacturer Part Number: C8051F131R
• Description: 8-bit Microcontrollers - MCU 128kB 100MIPS 8448B RAM
• Manufacturer: Silicon Labs

Specifications of C8051F131R

• Product Category: 8-bit Microcontrollers - MCU
• Core: 8051
• Data Bus Width: 8 bit
• Maximum Clock Frequency: 100 MHz
• Program Memory Size: 128 KB
• Data Ram Size: 8.25 KB
• On-chip Adc: Yes
• Operating Supply Voltage: 2.7 V to 3.6 V
• Package / Case: TQFP-64
• Mounting Style: SMD/SMT
• A/d Bit Size: 10 bit
• A/d Channels Available: 9
• Data Rom Size: 64 KB
• Interface Type: I2C, SMBus, SPI, UART
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Number Of Programmable I/os: 32
• Number Of Timers: 16 bit
• Processor Series: C8051
• Program Memory Type: Flash
• Factory Pack Quantity: 500
• Supply Voltage - Max: 3.6 V
• Supply Voltage - Min: 3 V

C8051F120/1/2/3/4/5/6/7
C8051F130/1/2/3
The PnMDOUT registers control the output modes of the port pins regardless of whether the Crossbar has
allocated the Port pin for a digital peripheral or not. The exceptions to this rule are: the Port pins connected
to SDA, SCL, RX0 (if UART0 is in Mode 0), and RX1 (if UART1 is in Mode 0) are always configured as
Open-Drain outputs, regardless of the settings of the associated bits in the PnMDOUT registers.
18.1.3. Configuring Port Pins as Digital Inputs
A Port pin is configured as a digital input by setting its output mode to “Open-Drain” and writing a logic 1 to
the associated bit in the Port Data register. For example, P3.7 is configured as a digital input by setting
P3MDOUT.7 to a logic 0 and P3.7 to a logic 1.
If the Port pin has been assigned to a digital peripheral by the Crossbar and that pin functions as an input
(for example RX0, the UART0 receive pin), then the output drivers on that pin are automatically disabled.
18.1.4. Weak Pullups
By default, each Port pin has an internal weak pullup device enabled which provides a resistive connection
(about 100 k  ) between the pin and V
logic 1 to the Weak Pullup Disable bit, (WEAKPUD, XBR2.7). The weak pullup is automatically deactivated
on any pin that is driving a logic 0; that is, an output pin will not contend with its own pullup device. The
weak pullup device can also be explicitly disabled on any Port 1 pin by configuring the pin as an Analog
Input, as described below.
18.1.5. Configuring Port 1 Pins as Analog Inputs
The pins on Port 1 can serve as analog inputs to the ADC2 analog MUX on the C8051F12x devices. A Port
pin is configured as an Analog Input by writing a logic 0 to the associated bit in the PnMDIN registers. All
Port pins default to a Digital Input mode. Configuring a Port pin as an analog input:
Note that the output drivers on a pin configured as an Analog Input are not explicitly disabled. Therefore,
the associated P1MDOUT bits of pins configured as Analog Inputs should explicitly be set to logic 0
(Open-Drain output mode), and the associated Port1 Data bits should be set to logic 1 (high-impedance).
Also note that it is not required to configure a Port pin as an Analog Input in order to use it as an input to
ADC2, however, it is strongly recommended. See the ADC2 section in this datasheet for further informa-
tion.
240
1. Disables the digital input path from the pin. This prevents additional power supply current from
2. Disables the weak pullup device on the pin.
3. Causes the Crossbar to “skip over” the pin when allocating Port pins for digital peripherals.
being drawn when the voltage at the pin is near V
a logic 0 regardless of the voltage at the Port pin.
DD
. The weak pullup devices can be globally disabled by writing a
Rev. 1.4
DD
/ 2. A read of the Port Data bit will return