error in serial communication

hi,all i use the following codes to transimit data from matlab to 8051 mcu

s=serial('com3','baudrate',9600);
>> fopen(s)
>> fwrite(s,10101010,'int8')

and codes for 8051 to receive data via serial port is

org 2000h
mov tmod,#20h
mov th1,#0fah
mov scon,#50h
setb tr1
here:jnb ri,here
mov a,sbuf
mov p1,a
clr ri
sjmp here
end

the problem when i displayed received data it appear on led 11111110 what the wrong plzzzzzz help at least idea

Answer 1

[Walter Roberson]

In your command

fwrite(s,10101010,'int8')

you are asking to have decimal 10101010 converted to int8, and transit that. The effect would be as if you had used

fwrite(s, int8(10101010), 'int8')

which, due to the saturation properties of int8, would be equivalent to

fwrite(s, int8(127), 'int8')

High bit is 0, but low bit is transmitted first in serial, so the bit order across the wire would be 11111110 .

Remember, 10101010 is a decimal number, ten million, one hundred and one thousand, and ten.