Problem reading zeros from serial port

I am reading binary data from FPGA through COM port. Here is the code I am using

delete(instrfindall);
clear s

s = serial('COM4'); %assigns the object s to serial port 
set(s, 'InputBufferSize', 256); %number of bytes in inout buffer
set(s, 'FlowControl', 'software');
set(s, 'BaudRate',115200 );
set(s, 'Parity', 'none');
set(s, 'DataBits', 8);
set(s, 'StopBit', 1);
set(s, 'Timeout',10);

fopen(s);
x = fread(s, 256, 'uint8');
fclose(s);

It reads all the values except zero. If a zero appears in the stream it discards that value and read the next value. If I send constant 0s it displays the warning "Warning: Unsuccessful read: The specified amount of data was not returned within the Timeout period."

Cam someone please help me solve this?