说明：  JTAG CPLD实现源代码，比用简单并口调试器快5倍以上。 以前总觉得简单的并口jtag板速度太慢，特别是调试bootloader的时候，简直难以忍受。最近没什么事情，于是补习了几天vhdl，用cpld实现了一个快速的jtag转换板。cpld用epm7128stc100-15，晶振20兆，tck频率5兆。用sjf2410作测试，以前写50k的文件用时5分钟，现在则是50秒左右。tck的频率还可以加倍，但是不太稳定，而且速度的瓶颈已经不在tck这里，而在通讯上面了。
(JTAG CPLD source code than the simple parallel debugger five times faster. Before feel simple parallel port JTAG board is too slow, especially when debugging Bootloader, simply intolerable. No matter recently, so VHDL tutorial for a few days, with cpld to achieve a rapid conversion of JTAG board. Cpld with epm7128stc100-15, 20 Katherine crystal, the frequency tck 5 trillion. Sjf2410 used for testing, before the document was made with 50k at 5 minutes, now it is about 50 seconds. Tck frequencies can also doubled, but not too stable, but the rate has not tck bottleneck here, and in the above communications.)