thanks HAl, I will try this one. I did some changes in the first posted program, this modified program runs ok at my Franklin Software, as a matter of fact, I can see TI register toogling true and false while the characters are sending to buffer, I can see them at buffer, the RI register always is true since begins the program. Please run this one at your PINNACLE SIMULATOR and see what happens. It's a fact that I need toogle ground & Vcc (twice) P3.0 pin RXD to begin the program works, is this correct ?
This program send ASCII characters to buffer, as I told you this runs ok at my simulator, I burned a EPROM with this one but is the same, no signals at pin 3.1 TXD. I was reading a book where says that the pulses in MODE 1 the data is sent by TXD and received by RXD, then why I can see them ?

ORG
LJMP MAIN
ORG 0023H
LJMP SPISR
ORG 0030H
MAIN:MOV SCON,#07AH
MOV IP,#038H
MOV TMOD,#20H ; TIMER 1 MODE2
MOV TH1,#0FDH ; 9600 BAUD RATE
SET TR1
MOV IE,#90H
MOV A,#20H
SJMP $

SPISR: PUSH PSW
CJNE A,#7FH, SKIP
MOV A,#20H
SKIP : MOV SBUF,A
INC A
CLR TI
POP PSW
RETI
END