编写程序，使8255端口A工作在方式0并作为输出口，端口B工作在方式1并作为输入口，则端口C的PC2成为选通信号输入端STBB，PC2成为中断请求信号输出端INTRB。

当B口数据就绪后，通过发STBB 信号来请求CPU读取端口B数据，并送A端口输出显示。

-Write a program to work in 8255 mode 0, port A as output port, the port operating in mode 1 and B as input port, the port C of PC2 as strobe input STBB, PC2 as an interrupt request signal output INTRB. When the B port data ready, the request by sending signals to CPU STBB read port B data, and sent A port output.