- 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
- :
- Product Forums
- :
- ColdFire/68K Microcontrollers and Processors
- :
- Setting clock speed higher than the model designates
Setting clock speed higher than the model designates
- Subscribe to RSS Feed
- Mark Topic as New
- Mark Topic as Read
- Float this Topic for Current User
- Bookmark
- Subscribe
- Mute
- Printer Friendly Page
Setting clock speed higher than the model designates
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
I just started getting this low level, but had a question about clock speeds that I can't seem to find and answer elsewhere.
If I am using a MC68332ACAG25 but have to use a MC68332ACAG20 in the future, is it possible to clock the AG20 up to 25MHz through any software means? Or is the AG20 effectively hard capped at this clock speed?
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
How lucky are you feeling?
Some chips are pretty forgiving. We once had a small batch of boards assembled with the wrong crystals and they were running at 1.5x their maximum rated clock frequency. Only noticed it because a DSP function wasn't working right due to the wonky sample rate.
You might get away with it, particularly if you're not at the edges of the temperature and voltage ranges, but I wouldn't do it on purpose in a commercial product. You might be chasing weird intermittent peripheral glitches, or it might just fail completely at some point.
Scott
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
Read the SIM chapter to see how these chips work. Basically you can either connect a 32,768Hz crystal and use the internal PLL to generate the clock (at whatever frequency you want) or you can generate the 16MHz, 20MHz, 25MHz (or anything you want) externally and feed that in.
External oscillators have to have very well controlled duty cycles, so the 32,768Hz option may be easier unless your system requires the frequency stability of a high speed clock.
There is no "frequency locking". Different grades of chip are guaranteed to run up to a specific speed. You can try overclocking, but if it fails or is unreliable, that's on you. You may be able to overclock over a limited temperature range. Or maybe not. Basically if you're doing this for a hobby, then you can overclock as much as you like. If you're making something for production or sale, then you can't guarantee it will work reliably if you overclock it.
The tables in the SIM chapter give the programming for different frequencies, and shade the sections that generate clock speeds above the limits in a different colour.
Tom
