upss ya. Sory...
But I have my final project at my college. I use 19600 as a baudrate. It works better then other baudrate. Its example code: Checking "at" via serial port:
;=======
$MOD51
org 00h
jmp main
org 23H
jmp rx
;reti
;sjmp septet_encoding
;====
org 0800h
main:
mov tmod,#020h ;timer1 mode2
mov th1,#0fdh ;19200 baudrae
mov scon,#050h ;mode seria8 bit uart
mov 87H,#80H ;;;SERIAL 19200
setb tr1 ;jalankan timer1
mov r0,#60h ;penunjuk tampilan
mov sp,#10h ;definisi lokasi stack
setb es
setb ea
;=================
;ngreset parameter
;persiapan jaur data
mov 7dh,#00h
at1:
acall delay
acall tx_at
acall delay
call cek_ok
call delay
call tx_smso
DEAD:
SJMP DEAD

delay:
push acc
push b
mov r3,#10
delay1:
mov acc,#0ffh
delay2:
mov b,#0ffh
djnz B,$
djnz acc,delay2
djnz r3,delay1
pop b
pop acc
ret

rx:
jb RI,rx_1
clr TI
reti
rx_1:
push psw
push acc
mov a,sbuf
mov a,sbuf
mov 75h,76h
mov 75h,77h
mov 77h,78h
mov 78h,79h
mov 79h,7Ah
mov 7Ah,7Bh
mov 7Bh,7Ch
mov 7Ch,7Dh
mov 7Dh,7Eh
mov 7Eh,7Fh
mov 7Fh,A
clr ri
; call balik
pop acc
pop psw
reti
;balik:
; MOV A,7FH
; mov sbuf,a
; ret
cek_ok:
mov a,7Dh
cjne a,#'K',belumkonek
mov a,7Ch
cjne a,#'O',belumkonek
mov a,7Fh
cjne a,#10,belumkonek
mov a,7Eh
cjne a,#13,belumkonek
mov p2,#00fh
ret
belumkonek:
mov p2,#00h
JMP AT1

tx:
clr es
mov sbuf,a
jnb ti,$
clr ti
setb es
ret
txdata:
clr a
movc a,@a+dptr
acall tx
inc dptr
djnz r4,txdata
ret
;data at-command
dat_at:
db 'AT',13,10
dat_atz: ;default configuration
db 'ATZ',13,10
dat_smso: ;switch device operator
db 'AT^SMSO',13,10
dat_cmgl4: ;daftar sms semua
db 'AT+CMGL=4',13,10
dat_cpmsme: ;seleksi sms memory=semua
db 'AT+CPMS=SM',13,10
dat_cmgd4: ;delete sms all
db 'AT+CMGD=4',13,10
dat_cmgr4: ;baca sms all
db 'AT+CMGR=4',13,10
dat_cmss1: ;kirim sms dr memori
db 'AT+CMSS=1',13,10
dat_cmss2: ;delete sms all
db 'AT+CMSS=2',13,10
dat_cmss3: ;delete sms all
db 'AT+CMSS=3',13,10
;=====
;pengiriman data serial
sendend1:
acall tx
mov a,#10
acall tx
ret
tx_at:
mov r4,#4
mov dptr,#dat_at
acall txdata
ret
tx_smso:
mov r4,#9
mov dptr,#dat_smso
acall txdata
ret
tx_cmgl4:
mov r4,#11
mov dptr,#dat_cmgl4
acall txdata
ret
tx_cpmsme:
mov r4,#11
mov dptr,#dat_cmgd4
acall txdata
ret
tx_cmgd4:
mov r4,#11
mov dptr,#dat_cmgd4
acall txdata
ret
tx_cmgr4:
mov r4,#11
mov dptr,#dat_cmgr4
acall txdata
ret
tx_cmss1:
mov r4,#11
mov dptr,#dat_cmss1
acall txdata
ret
end
;======
My project is not finish yet. But I guess its enough for checking the respon of "AT" command via serial port. Hope this help...
ADD: The serial port is correct, but pin 4 must be set low (conect with +3 to +25 volt,in order to m35i can send the data).