在你的MCU上運行RTOS時的硬件考慮

　　MCU來控制嵌入式系統在越來越多的功能。通常這些功能是實時的，需要定期的服務，以滿足系統的要求，響應，性能，或可靠性。通常，實時操作系統（RTOS）用于管理多個實時事件，以確保響應速度足以滿足系統要求。不是所有的MCU都適合舉辦一個實時操作系統，然而，所以回顧一些關鍵功能，允許或促進主機實時操作系統在一個特定的單片機的實時嵌入式系統的設計者很有用。

　　本文將回顧一些可用的關鍵特征對現代MCUs，幫助運行嵌入式系統需要實時操作系統時。這將有助于設計人員更有效地選擇一個MCU作為一個RTOS主機，并設計使用該MCU的嵌入式系統。

　　Managing real-time response

　　As control systems become more complicated， it is increasingly difficult to manage the various MCU functions with a simple control routine. With multiple events with different priorities， a single control loop that is constantly checking to see what event needs service becomes unwieldy. The control loop just cannot get to every function quickly enough. What is needed is a real-time approach to control， where all events can be serviced within their required response time.

　　Often an MCU can achieve better control over complex systems by responding to an event， either an internal MCU request triggered by a timer or an external event triggered by an I/O signal， using an interrupt. Interrupts can be prioritized so that the most important requests are processed first， and with modern MCU interrupt systems， response times can be very fast. Unfortunately， proving that all events will be handled with the required periodicity can be difficult. For example， if we need to make a series of analog-to-digital conversions， while receiving data over a USB port and computing a low-pass filter on the acquired analog data， figuring out the maximum sample rate for the conversion may be very difficult.