The Softer Option

　　微控制器的形狀和大小令人眼花繚亂的陣列，但他們都有一個共同點(diǎn)：他們的功能是由制造商定義。而他們的外設(shè)的設(shè)計(jì)盡可能靈活，經(jīng)常修改某些參數(shù)的能力，有的甚至允許新的功能被添加到軟件如Cypress半導(dǎo)體的PSoC家族，他們?nèi)匀痪哂泄潭〝?shù)量的資源，允許相對小的定制。正是由于這種固定的功能，大量的變種存在。

　　FPGAs，另一方面，是一個相對空白的畫布：他們的功能主要是由工程師使用他們幾乎無限的能力范圍選擇。正是這種自由的設(shè)計(jì)，使團(tuán)隊(duì)能夠整合許多不同的數(shù)字（和越來越多的模擬）功能成為一個單一的，基本上量身定制的設(shè)備，可以更好地適應(yīng)特定的設(shè)計(jì)。

　　Variations on a theme

　　Programmable logic has evolved far beyond the PLD; traditionally popular for providing ‘glue logic’ in relatively simple designs. The availability of processor cores in the form of IP means OEMs can now choose to add a microcontroller （MCU） in often the smallest of FPGAs. While they may not offer total freedom of design， adding a soft core can deliver even greater design consolidation than simple combinatorial gates.

　　However， perhaps even more significantly， microcontrollers in the form of soft cores are normally optimized by the manufacturer for specific FPGA families， which commercially allows those manufacturers to offer the cores free， with no up-front cost or royalty. It means that if you’re using an FPGA and it has spare capacity， you essentially get an MCU for free. Furthermore， because the cores have been optimized to run in what is often a high-performance FPGA fabric， they invariably deliver greater performance than their discrete counterparts.