ARM Technical Support Knowledge Articles

ARM website Product pages recommend CMSDK bit banding, but CMSDK TRM does not

Applies to: Cortex-M System Design Kit (CMSDK), Cortex-M0, Cortex-M0Plus


The Cortex-M System Design Kit provides a bit banding wrapper for Cortex-M0 and Cortex-M0+. This implements the same functionality as the optional bit banding feature in Cortex-M3 and Cortex-M4. This provides a simple method of making a Cortex-M0/M0+ system compatible with a pre-existing Cortex-M3/M4 design in respect of bit-wise access to memory and peripherals.

Because the wrapper is located between the processor and the bus interconnect, it may introduce extra cost:

  • Longer timing paths on AHB interconnect and therefore a reduction in the maximum clock frequency.

  • Higher power consumption.

  • Larger design size.

If there is not a requirement for exactly matching the Cortex-M3/M4 behavior of a previous design, these costs might be reduced or eliminated by redesigning the slave to implement bit-wise behavior within the slave itself rather than using the bit band wrapper.

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