内嵌BRAM设计LIFO堆栈。功能如下：具有先进后出的堆栈功能。此LIFO堆栈具有两个按键（write， read），按下write键后，开始输入数据data0-data3；按下read键后，7段数码管开始倒序显示data3-data0（十进制）。（内加vga显示数据，不附带图片）-Embedded BRAM design LIFO stack. Function as follows: after having advanced out of the stack functionality. This LIFO stack has two buttons (write, read), press the write key to start entering data data0-data3　press the read key, 7-segment display start descending data3-data0 (decimal). (Within plus vga display data, not with pictures)