- Forums
- Product Forums
- General Purpose MicrocontrollersGeneral Purpose Microcontrollers
- i.MX Forumsi.MX Forums
- QorIQ Processing PlatformsQorIQ Processing Platforms
- Identification and SecurityIdentification and Security
- Power ManagementPower Management
- Wireless ConnectivityWireless Connectivity
- RFID / NFCRFID / NFC
- Advanced AnalogAdvanced Analog
- MCX Microcontrollers
- S32G
- S32K
- S32V
- MPC5xxx
- Other NXP Products
- S12 / MagniV Microcontrollers
- Powertrain and Electrification Analog Drivers
- Sensors
- Vybrid Processors
- Digital Signal Controllers
- 8-bit Microcontrollers
- ColdFire/68K Microcontrollers and Processors
- PowerQUICC Processors
- OSBDM and TBDML
- S32M
- S32Z/E
-
- Solution Forums
- Software Forums
- MCUXpresso Software and ToolsMCUXpresso Software and Tools
- CodeWarriorCodeWarrior
- MQX Software SolutionsMQX Software Solutions
- Model-Based Design Toolbox (MBDT)Model-Based Design Toolbox (MBDT)
- FreeMASTER
- eIQ Machine Learning Software
- Embedded Software and Tools Clinic
- S32 SDK
- S32 Design Studio
- GUI Guider
- Zephyr Project
- Voice Technology
- Application Software Packs
- Secure Provisioning SDK (SPSDK)
- Processor Expert Software
- Generative AI & LLMs
-
- Topics
- Mobile Robotics - Drones and RoversMobile Robotics - Drones and Rovers
- NXP Training ContentNXP Training Content
- University ProgramsUniversity Programs
- Rapid IoT
- NXP Designs
- SafeAssure-Community
- OSS Security & Maintenance
- Using Our Community
-
- Cloud Lab Forums
-
- Knowledge Bases
- ARM Microcontrollers
- i.MX Processors
- Identification and Security
- Model-Based Design Toolbox (MBDT)
- QorIQ Processing Platforms
- S32 Automotive Processing Platform
- Wireless Connectivity
- CodeWarrior
- MCUXpresso Suite of Software and Tools
- MQX Software Solutions
- RFID / NFC
- Advanced Analog
-
- NXP Tech Blogs
- Home
- :
- General Purpose Microcontrollers
- :
- Kinetis Microcontrollers
- :
- VBAT and 32.76kHz oscillator doubt
VBAT and 32.76kHz oscillator doubt
- Subscribe to RSS Feed
- Mark Topic as New
- Mark Topic as Read
- Float this Topic for Current User
- Bookmark
- Subscribe
- Mute
- Printer Friendly Page
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
I don't understand why while the TWR-K20D50 board is powered by USB (J36 is open) and no battery is inserted, the demo program works only if J35 is closed.
From the datasheet of the microcontoller I have understood that Vbat powers only the RTC clock but the test on the evaluation board shows the opposite: is Vbat necessary for the system (and not only for the RTC module) in order to work properly?
What about the 32.768kHz crystal? Is it necessary if I don't want to power the RTC oscillator and if a 8MHz resonator feeds the system clock?
Solved! Go to Solution.
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
Hello Gabriele,
K20D50 does not require VBAT to operate and you can use only the 8MHz crystal/resonator when RTC is not used, but TWR-K20D50M Demo software is using the RTC module, and any attempt to access an RTC registers when VBAT is powered down, will result in a bus error and causing the MCU to reset. If you have a terminal connected to the TWR-K20D50M you will see this message when VBAT is disconnected ****default_isr entered on vector 3*****.
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
Hello Gabriele,
K20D50 does not require VBAT to operate and you can use only the 8MHz crystal/resonator when RTC is not used, but TWR-K20D50M Demo software is using the RTC module, and any attempt to access an RTC registers when VBAT is powered down, will result in a bus error and causing the MCU to reset. If you have a terminal connected to the TWR-K20D50M you will see this message when VBAT is disconnected ****default_isr entered on vector 3*****.
