哪個ARM皮質CPU適合你的下一個基于單片機的應用程序？

　　基于ARM的CPU在MCU世界普遍存在，并且經常有幾個可用的來自同一個MCU的供應商。每個ARM CPU已經優化了一類特定的處理要求，從低端功率受限的應用到高功率性能優化，雙核應用。最流行的ARM CPU今天在MCU設備似乎是皮質CPU。你如何決定哪一個ARM皮質CPU是正確的一個應用程序？讓我們探討的主要差異，一些比較流行的基于MCU的皮層看例子的實現，將幫助你決定哪一個是你的下一個設計。

　　Many options

　　It’s not unusual to find many different ARM Cortex CPUs within a single MCU family. The Cortex CPU and its optional extensions address a variety of application needs， but all have backward-compatible instruction sets， as illustrated in Figure 1. Starting with the Cortex-M0/M0+/M1 family， the instruction set is targeted for general-purpose data processing and IO tasks. The Cortex-M3 CPU adds advanced-data processing and bit-field manipulation instructions that speed up more complex control and general-purpose computational tasks. The Cortex-M4 CPU adds Digital-Signal processing （DSP） instructions and offers Single-Instruction Multiple-Data （SIMD） operations where the same data-processing instruction can operate on multiple-data sources at the same time. These specialized capabilities can dramatically accelerate complex data-processing tasks， like those found in audio and video applications. The Cortex-M4 CPU can also add a Floating Point Unit （FPU） when performance and precision are both important elements for the target algorithm. Analog sensing and motor control， for example， often use floating point for its precision， but high performance is required for fast-control loop closure.