这是用M16做的jtag与stk500（正确说应该是ISP）合二为一的，用PC6脚是否是低电平判断是jtag还是stk500。-This is the M16 to do with the JTAG with stk500 (correctly said that it should be ISP) combined with a pin PC6 is to determine whether low-level JTAG or stk500.