The Softer Option

　　The Softer Option

　　微控制器的形状和大小令人眼花缭乱的阵列，但他们都有一个共同点：他们的功能是由制造商定义。而他们的外设的设计尽可能灵活，经常修改某些参数的能力，有的甚至允许新的功能被添加到软件如Cypress半导体的PSoC家族，他们仍然具有固定数量的资源，允许相对小的定制。正是由于这种固定的功能，大量的变种存在。

　　FPGAs，另一方面，是一个相对空白的画布：他们的功能主要是由工程师使用他们几乎无限的能力范围选择。正是这种自由的设计，使团队能够整合许多不同的数字（和越来越多的模拟）功能成为一个单一的，基本上量身定制的设备，可以更好地适应特定的设计。

　　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.