When I configure uart communication of ADE7169 device(enhanced 8052 core),I encountered a problem that comment out or not the code (MOV PCON,#80H ;Here is not wor)(line 5) does not affect uart's baud.But as document description,SMOD (PCON MSB) will double baudrate if it is assert.I am sure I have assert SMOD ,because when I monitor sfr's state,i find this bit is set to one. Who know why?who can help me? Thank you in advanced! My code is follow: MOV RCAP2L,#0AFH ; MOV RCAP2H,#0FFH ; MOV TL2,#0AFH ; MOV TH2,#0FFH ; ;MOV PCON,#80H ;Here is not work MOV T2CON,#34H ;SET timer2 MOV SCON,#50H ;MODE1 and ENABLE RECV SETB EA ;GLOBAL INTERRUPT ENABLE SETB ES ;SERIAL INTERRUPT ENABLE