PCB布线的经验之谈 。 布线的限制，重点，以及注意方向-PCB layout of experience. Wiring constraints, focus, and pay attention to the direction of

CPLD的烧录程序，保证与单片机数据互通，提供串口引脚约束。-CPLD burning procedures to ensure that the data exchange with the microcontroller, providing serial pin constraints.