已知在内部RAM30好，31H中存放两个单字节数分别是21H和43H，要求将两数分别拆开后按半字节的形式分别存放在40H开始的内部RAM中，并将其高位清零，要求低字节存放在低地址中-Well known within the RAM30, 31H is stored in the number of two-byte 21H, respectively, and 43H, respectively required apart the two half-byte 40H are stored in the form of starting the internal RAM, and high cleared, requiring low byte is stored at low address