可以用于sst89e58rd串口的测试 ;串口程序 ORG 0000H; AJMP MAIN; ORG 0023H; AJMP USART; ORG 0030H; MAIN: CLR ES; CLR TR1; MOV TMOD, #020H; MOV PCON, #00H; MOV TCON, #0B0H; MOV SCON, #050H; MOV TH1, #0FAH; MOV TL1, #0FAH; MOV IP, #010H; SETB REN; CLR TI; CLR RI; CLR