將第二MCU引入嵌入式設計

　　有很多理由在你的設計中添加第二個MCU，一旦你做了很多錯誤，就避免了。本文在考慮沿途的缺陷時考慮了參數和選項。

　　隨著處理器可用的今天，品種繁多，有很多原因，你會發現它是添加新的功能引入第二單片機的應用更具成本效益的選擇（MCU）或微處理器（MPU）為你的設計而不是試圖一次完成所有的任務，更高性能的處理器：

　　成本：遷移到一個更高性能的系統中，微處理器可以比添加8位或16位MCU來承擔額外的負載有更高的成本差異。

　　電源：而不是花費的權力，使主要應用處理器不斷打開自己來執行一個相對簡單的操作，如監測一個傳感器銀行或檢查是否有一個按鍵被按下，一個8位處理器可以用來執行這些任務。本質上，8位處理器是一個“電源門”，它只允許主處理器在需要注意的事件發生時休眠并喚醒它。這是特別有效的電阻和表面電容式觸摸屏。

　　確定性：包括計算密集型任務（如動畫或音頻）的用戶界面（UI）功能可以強調系統的實時確定性行為。第二個MCU可以承擔所有的“實時”UI責任，而不是威脅像電機控制這樣的關鍵任務的可靠性。

　　Diversity： Many systems can benefit from a modular design. For example， a display module can be implemented with a different processor to provide additional graphics， or streaming video capabilities. By taking a modular approach， the main application code does not need to be changed to add new features to the system or to support different models.

　　Simplicity： A product line may offer a wide variety of options. For example， a product may have four screens， three keyboards， and three connectivity options. When a single processor is used， the design team has to maintain， test， and verify a separate code version for each possible variant （4x3x3=36 distinct variants）。 When a secondary processor is used to implement a new function， maintenance is required only for each option （4+3+3=10）。 Note that with the first option， the entire system needs to be tested and verified with every variant， a complex and time-consuming process. When using the second option， the main application code only needs to be verified once. Each of the options can be verified separately and with significantly less complexity.

　　Conservation of I/O： An MCU can appear to be several devices over an interface by responding to several addresses. For example， the main application processor could issue a command to turn on a fan which is intercepted by an MCU serving as a virtual hub. This is an effective way to conserve I/O on the main application processor since only one communication peripheral is required to read and control multiple devices.

　　Certification： Changing the user interface or introducing a new interface like Wi-Fi to the main system requires the entire design to be recertified for some markets. Implementing these functions as an add-on module with a separate processor simplifies the recertification process， significantly accelerating both development and time-to-market.