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Real-time Linux supports MMU-ful ColdFire microcontroller

Sep 25, 2006 — by LinuxDevices Staff — from the LinuxDevices Archive — 5 views

FSMLabs is shipping a real-time Linux development kit for Freescale's first-ever MMU-equipped ColdFire microcontroller. RTLinuxPro 2.2 for the MCF5485 targets SCADA (supervisory control and data acquisition), instrumentation, and non-traditional control applications, and is optionally available with Eclipse-based tools, according to the company.

Freescale announced the MCF548x, along with the MCF547x, in May of 2004. The chips were touted as the first ColdFire microcontrollers to support full Linux, rather than being limited to uClinux, a version of the OS adapted for MMU-less processors.

MCF5485 diagram
(Click to enlarge)

FSMLabs says that its RTLinux kit for the MMU-ful ColdFire controllers offers adequate real-time performance — at clock speeds as low as 200MHz, and system bus speeds of only 100MHz. The kit include “patented hard real-time virtualization technology” that combines the RTCore real-time kernel with an embedded Linux or BSD client OS that is “completely preemptible by time-critical code,” FSMLabs says. This is said to enable real-time tasks such as motor control, data acquisitions, and real-time networking, while still taking advantage of the enterprise software platform provided by the Linux OS.

In addition to a complete Linux-based, dual-kernel OS and development tools, the RTLinux kit includes real-time DIO (digital I/O) and Canbus drivers, FSMLabs says. The DIO driver “can easily drive a 25KHz square wave!” according to the company. (For more about how the company uses analog square waves to illustrate real-time performance characteristics, be sure to read this whitepaper here at

Claimed real-time characteristics for RTLinux Pro on a 200MHz MCF5485 are as follows:

  • Worst case interrupt latency — 44 microseconds
  • Worst case Scheduling jitter (worst case interrupt latency plus context switch plus scheduling overhead) — 90 microseconds
  • Worst case context switch — 56 microseconds

FSMLabs principal architect Michael Barabanov stated, “RTLinux allows real-time developers to conserve power and minimize bill of material costs without needing to go back to a primitive bare-bones software environment. The performance is outstanding for a 200MHz controller.”

Renee Mitchell, operations manager for Freescale's consumer and industrial microcontroller divisions, stated, “The combination of ColdFire controllers and RTLinux provides an embedded enterprise platform that helps control system developers leverage existing middleware and utilities and focus on their applications instead of low-level OS issues.”


RTLinuxPro 2.2 for ColdFire controllers is available immediately. Also available is an Eclipse-based IDE.

Embedded developer services provider TimeSys also supports the MCF548x.

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