Questions:

A. What is Errata RMU_E103

B. What devices are affected?

C. How can I prevent this issue from affecting my application?

D. Are there plans to fix this issue?

Answers:

A.

Erratum RMU_E103 describes an issue with certain Series 0 EFM32 devices. Affected parts see a gap in the coverage of the brown-out and power-on reset sources around 1.3V . The exact gap in reset coverage will be part specific if present at all. If an affected device is operating in this problematic VDD range, the device will attempt to start up while well below the tested supply voltage for the microcontroller.

The device takes a short amount of time to start up. For a typical part at normal voltages this is 163 µS. If the startup succeeds, the device will then attempt to execute code, but may not be able to do so at low voltage. At this low voltage neither a successful startup or successful code execution is guaranteed.

Note that during fast voltage ramps, e.g. power-on and power down events, VDD will not be at a problematic voltage long enough for the device to start up. However, if VDD is held at around 1.3V for a sufficient duration, the device may enter this undefined state where code is being executed below tested voltages.

The workaround to this issue is to assert a pin reset during the low VDD event. If a pin reset is asserted, the device cannot attempt to start up. The reset pin should be driven low prior to VDD falling below the BOD reset threshold.

B.

RMU_E103 is an erratum that effects some devices from the following EFM32 Series 0 products:

• EFM32 Zero Gecko
• EFM32 Happy Gecko
• EFM32 Wonder Gecko
• EFM32 Leopard Gecko
• EFM32 Tiny Gecko (Series 0 only)
• EZR32 Happy Gecko
• EZR32 Wonder Gecko
• EZR32 Leopard Gecko

This erratum does not affect EFM32 Gecko, Giant gecko, or any EFM32 Series 1 devices.

C.

Steps can be taken to both detect if RMU_E103 is occurring on a specific device, and to prevent code from executing at low voltage.

• To detect a gap in reset source coverage, Measure the current consumption of the device while gradually lowering VDD. If the device attempts to start up at low voltage, current consumption will increase. The diagram below shows an example VDD waveform that can test for code execution at low voltage and the corresponding spike in current consumption. Note that the current and voltage values are approximate and will vary across parts, applications, and environments.

Figure 1. VDD Test for RMU_E103 Current Consumption

• To avoid code execution at low voltage, avoid slow VDD ramps during normal operation. If the application is likely to experience a slow VDD ramp or see low supply voltage for any significant duration of time, use an external device or user input to assert a pin reset at some VDD level > 1.96V (with sufficient time to engage the internal reset before VDD reaches 1.96V).

Questions:

A. What is Errata RMU_E102?

B. What devices are affected?

C. How can I prevent this issue from affecting my application?

D. Are there plans to fix this issue?

Answers:

A.

Erratum RMU_E102 describes an issue with certain Series 0 EFM32 devices. Affected parts may see voltage regulator failure when subjected to the following scenario:

1. VDD begins to fall due to some external event
2. VDD and Regulator output (DECOUPLE) voltage decay to 0.8-1.2V
3. Power supply to VDD is restored and VDD returns to a nominal value  prior to VDD and DECOUPLE reaching < 0.8V 

In this type of sequence mentioned above , the voltage regulator may fail to re-initialize. If this occurs, the DECOUPLE pin will continue to decay to 0V, even after VDD has recovered. In this state, the core logic is not powered, and the device will be unable to execute code or respond to a pin reset. An affected device will successfully recover from this state if power cycled.

Additionally, if a pin reset is applied prior to the Brown out detector (BOD) asserting reset, the regulator will always re-initialize successfully. The BOD threshold varies between 1.74-1.96V, so a pin reset should be asserted before VDD drops below 1.96V. The pin-reset should be held low until VDD is >1.98V, which is the maximum power-on reset threshold.

The diagrams below demonstrate an example VDD waveform that can cause the regulator initialization to fail.

Figure 1. VDD Decay and Recovery

This figure shows the proper recovery sequence, or what will happen to a working device (not affected by RMU_E102) when VDD falls to 0.9V. Here, the regulator restarts after VDD is restored, and the DECOUPLE voltage returns to 1.8V.

Figure 2. VDD Decay and DECOUPLE failure

This figure shows the failure mode for a device affected by RMU_E102 when VDD falls to 0.9V. As you can see the regulator fails to re-initialize properly, and the DECOUPLE voltage continues to fall until reaching 0V. At this point a power-on reset must be performed to recover the device.

As mentioned above, there are two workarounds to the issue.

• For a device that is already in lock-up, perform a power cycle to recover to a normal state. To do this VDD must be driven to 0V before powering back on.
• For a device that may experience a drop in VDD to 0.8-1.2V, use an external device or user input to assert a pin reset at some VDD level > 1.96V (with sufficient time to engage the internal reset before VDD reaches 1.96V). Additionally, the reset should be held low until power is reconnected and VDD is greater than 1.98V.

B.

RMU_E102 is an erratum that effects some devices from the following EFM32 Series 0 products:

• EFM32 Zero Gecko
• EFM32 Happy Gecko
• EFM32 Wonder Gecko
• EFM32 Leopard Gecko
• EFM32 Tiny Gecko (Series 0 only)
• EZR32 Happy Gecko
• EZR32 Wonder Gecko
• EZR32 Leopard Gecko

This erratum does not affect EFM32 Gecko, Giant Gecko, or any EFM32 Series 1 devices.

C.

To avoid issues caused by RMU_E102, the following precautions should be taken.

• Avoid and check for intermittent battery or power supply connections to VDD. The issue was originally discovered in situations where a loose battery connection during assembly caused VDD to repeatedly drop to ~.9V and then recover to a nominal value. This represents a worst-case scenario for inducing RMU_E102, as multiple VDD disconnections occurred within a very short time frame.
• If your application is likely to experience frequent disconnects from the power supply, ensure that the reset pin is driven low prior to disconnecting.

Question:

What causes the L121 Improper Fixup error in Keil C51? How can I fix it?

Answer:

The most common cause is that, when the code was compiled, the compiler assumed functions were going to be close enough together to use the ACALL instruction, which can only jump 2k from its current destination. However, if the linker places functions farther apart than this, this fixup error occurs.

You can resolve this issue by changing the Memory Model setting in the Compiler to Large (program size 64k).

Question:

What is the largest capacitor value that I can place as a load on a GPIO pin?

Answer:

The relevant specification to determine the maximum capacitance on a pin is the maximum amount of current that the pin can sink or source. This is typically +/- 100 mA.

If you consider an infinite capacitance on a gpio to ground, this effectively creates a short between the pin and ground. In certain drive strength modes, a gpio can tolerate this condition indefinitely, as it would not be able to supply more current than the maximum.

For example, on EFM32LG devices, a pin can sink or source 100 mA, but the pin, when in DRIVEMODE = STANDARD, can only source 40 mA before the voltage at the pin is driven to zero (see the output current diagrams in the GPIO section of the datasheet) . So, in a short-to-ground event, the pin would source 40 mA indefinitely. In this case, when DRIVEMODE = STANDARD, or a lower setting, even an infinite capacitor would not violate the GPIO specifications, so any amount of capacitance is acceptable.

However, this same device, in DRIVEMODE = HIGH, can potentially source more than 100 mA under a short condition, which would damage the pin. In this case, some method for current limiting should be implemented to prevent damage to the device.

Problem

I have an EFM32 Development Kit with an MCU Plugin Board (e.g. EFM32WG-DK3850). Simplicity Studio detects the Mainboard but not the MCU Plugin Board (including the MCU). How can Simplicity Studio detect the MCU on this board, so I can start a debug session?

Solution

For older boards such as MCU Plugin Boards for EFM32 Development Kits, the user must manually specify the target MCU part number in Simplicity Studio before it can connect/debug the MCU.

Instructions on how to manually specify the target MCU part number:

1. In the Simplicity Studio Launcher, Debug Adapter pane, right click J-Link Silicon Labs > Device Configuration.

2. In the Device Hardware tab, under Boards, add your Plugin Board (e.g. “EFM32 Wonder Gecko DK MCU Plugin Board…”) and the Target Part should auto-populate. Click OK.

3. The Debug Adapters pane should now show the MCU part number. And Simplicity Studio is now setup to debug the board.

After manually specifying the MCU target part number in Studio, the IDE can start a debug session.

Question:

What does NRND really mean and what should the take away be if comparable or replacement devices have the same longevity commitment?

Answer: 

NRND typically means that we anticipate or that we've seen a decline in customer sales for a given device and thus it is unlikely that we will continue to produce this device beyond our longevity commitment.

Many of our 8-bit devices have the same longevity commitments but are in full production and do not bare the NRND label. This usually indicates that the device continues to be purchased in large quantities by our distributors/customers and as of now, the device is in continuous production to keep up with demand. This does not guarantee production beyond our longevity commitment, as we cannot predict the market through that date, but the larger customer base is a good indicator that we may continue to support this device beyond our initial commitment.

For a look at our 8-bit longevity commitment, you can visit this link https://www.silabs.com/products/mcu/8-bit/longevity-commitment.

Question: How do I debug when using Gecko Bootloader?

Answer: 

The debug plugin provides the bootloader with support for debugging output. If the plugin is configured to enable debug prints, short debug messages will be printed over Serial Wire Output (SWO), which can be accessed in multiple ways, including using Simplicity Commander, and by connecting to port 4900 of the Wireless Starter Kit TCP/IP interface.

Below are the steps to enable debug prints for the gecko bootloader

1. Configure the serial printing option in the Hardware Configurator of the gecko bootloader. Options on setting up the serial printing can be found here - https://www.silabs.com/community/wireless/zigbee-and-thread/knowledge-base.entry.html/2017/12/03/setting_up_serialou-fJAC

2. Turn on the debug option in the utility plugin of the .isc file of the bootloader and enable debug prints option in the plugin. This will enable the debugging in the bootloader.

Question: What are the reserved reset-reason codes for custom Gecko Bootloader usage?

Answer:

The first word of SRAM is used as shared memory between the bootloader and the application to flag the reason for a reset. The different possible reset reasons are defined in the Reset Information part of the Application Interface, in the file btl_reset_info.h.

For custom reset reasons it is recommended to set the high bit in order to be “far away” from Silicon Labs codes, i.e. 0x8000 or higher

Note:  0xC33C & 0xF00F reset codes are already used by Silicon Labs.

Question:

Why do I receive syntax errors in Simplicity Studio when defining an interrupt? The code compiles and works correctly, but declaring an interrupt, such as this one, gives a syntax error in Studio:
 

void Timer2_ISR (void) interrupt 5
{
// ISR code
}

Answer:

This occurs since Simplicity Studio uses a generic C syntax parser when looking for syntax errors in code. It doesn't understand compiler-specific C code, like that used by Keil C51 to define an interrupt function - the 'interrupt' keyword and interrupt number after the function declaration aren't standard C, so it throws a syntax error. Keil, however, when the project is compiled, understands this syntax and compiles the code correctly.

We have a work-around for this visual error by the way of macros in si_toolchain.h. If you use the SI_INTERRUPT(name, vector) macro, it will generate different declarations based on which tool is viewing the code. If __SLS_IDE__ is defined (that is, if the Simplicity Studio parser is looking at the code, it omits the interrupt vector number from the actual declaration. If Keil C51 is viewing the code, it places the vector number in the correct location for Keil to compile it correctly.

For example, if we used the following:
 

SI_INTERRUPT(INT1_ISR, 2)

In the IDE, this would generate:
 

void INT1_ISR (void)

But, for C51, this would generate:
 

void INT1_ISR (void) interrupt 2

This would eliminate the syntax error, but still allow Keil to compile the interrupt correctly.