In some cases, it is desirable to use the integrated charge pump when operating in the low power modes to power certain peripherals, such as the Real Time Clock (RTC). The SiM3L also integrates a missing clock detector that detects an RTC0 Oscillator Fail event when the RTC0 Missing Clock Detector is enabled and the RTC0OSC falls below the missing clock detector trigger frequency. When enabled, the charge pump powers the RTC and also uses the RTC clock as its pump clock to generate the voltage. If the RTC has a failure (such as losing the clock), the charge pump will also fail, thereby disabling power to the RTC. It is expected that firmware must disable the charge pump, restart the RTC, then re-enable the charge pump once the RTC is up and running.
The 5VDIFF mode can be used for differential signals (-2.5V to 2.5V) or single ended signals (0V to 2.5V). The value of the LSB does not change between these modes.
The reference is created by using an internal reference of 0.83V with a voltage divider of 1/6. This results in the measured signal being effectively compared to a 5V reference. The input to the ADC pin is still limited by the supply rails.
The GPIO slew rate setting is only available on EFM32JG, EFM32PG and EFR32.
The slew rate can be applied to pins on a port-by-port basis and is setup by SLEWRATE and SLEWRATEALT fields (0-7, higher values represent faster slew rate) in GPIO_Px_CTRL register.
1. Extended the baud rate divider to a 20-bit value, with a 15-bit integral part and a 5-bit fractional part. 2. In addition to PRS RX input, PRS CLK input is added.
3. Automatic baud rate detection.
4. Hardware flow control.
5. Debug halt.
6. New 8-bit timer to create timing for RX timout, break detection response timeout and RX enable delay.
How can I avoid "ground bounce" when using the SiM3U1xx or SiM3C1xx high drive I/O?
Answer
Our high current drivers have both programmable current limiting and four levels of programmable slew rate, which can mitigate the effects of ground bounce. If you set the slew rate limiting to the slowest setting, you will have no ground bounce issues if the MCU is properly grounded and you are driving a capacitive (non-inductive) load.
How many I/O can concurrently drive 300mA on SiM3U1xx?
Answer
Our devices can sink a maximum of 300 mA and source a maximum of 150 mA. The maximum sink or source for all I/Os on one supply is 400 mA. In other words, all I/Os in source mode must total less than 400 mA and all I/Os in sink mode must total less than 400 mA.
Which Silicon Labs STKs are mbed enabled and how can I tell?
Answer
All of the Silicon Labs EFM32 STKs support the mbed eco-system. After connecting the USB cable for the debug interface you should see a new Mass Storage drive created in Windows. If the drive is not displayed, select the Kit Manager in the Simplicity Studio tile screen and update the STK firmware. Once complete the drive should appear.
Pearl and Jade Gecko devices integrate a crypto accelerator. What is the best way for me to take advantage of the accelerator and implement my own cryptography?
Answer
The crypto accelerator significantly reduces the clock cycles required to implement standard crypto algorithms. Since advanced cryptography systems tend to be very complex and the development time to create such systems can be very long, Silicon Labs recommends using a standard set of libraries that have been proven in the industry. ARM provides the mbedTLS libraries (formerly PolarSSL) that support many of the standard encryption/decryption algorithms and cipher modes in wide use today. These libraries can be used "stand-alone" and do not need to use the mbed platform and online services.
Since the mbedTLS libraries do not have any awareness of the crypto accelerator, we have provided our own crypto libraries to be used with the mbedTLS libraries. In order to take advantage of the crypto accelerator the mbedTLS libraries, based on compile time options, will instead use the Silicon Labs libraries that offload the computationally intensive crytpo algorithms from the CPU to the crypto engine, significantly increasing performance while reducing power consumption.
Several example projects are included in the Simplicity Studio tools to illustrate how to use the CRYPTO module for both symmetric (CBC-AES) and asymmetric (ECDSA) encryption. In addition, application note AN0955: CRYPTO covers the different libraries and their uses.
32-bit Knowledge Base
SiM3L cannot restart the Real Time Clock (RTC) when using the charge pump
5V differential reference on EFR32/EFM32JG/EFM32PG
GPIO drive strength
GPIO slew rate
GPIO_IntConfig() function is deprecated
What's new in the EFM32 Gemstone/EFR32 USART?
Avoiding “ground bounce” with SiM3U1xx/SiM3C1xx high drive I/O
How many I/O can concurrently drive 300mA on SiM3U1xx?
Mbed support for EFM32 STKs
Crypto Acceleration in Pearl and Jade Gecko