编写子程序，完成的功能是将DL中的2位十六进制数转换为对应ASCII码。

说明：入口参数AL=待转换的2位十六进制数

　　出口参数DX=转换后的ASCII码，（高字节对应高位、低字节对应低位）-Subroutine prepared to complete the function is to DL in the two hexadecimal digits is converted to the corresponding ASCII code. Descr iption: imported parameter AL = pending conversion hexadecimal number two export parameters DX = converted ASCII code (high byte corresponds to high and low bytes correspond to low)