Code:
Flash_Byte_Modify:
 ' assumes address , length ( upto 256bytes )
 ' assumes sector 0 is not protected
   SDC_sector = 0
   gosub Flash_Sec_Erase  ' erase sector 0
   SDC_address.byte2 = 0  ' use sector 0,instead of given sector , but use given page, byte length  
   gosub Flash_write      ' Write the the changed data to sector 0
 
   if SDC_page > 0  and SDC_page <255 then  ' find the pages to copy 
   SDC_address.byte2 = 0 
   SDC_address.byte1 = SDC_page
   if  Data_Length < 255 then 
     SDC_address.byte0 = SDC_byte +1 -
well not far , this is the start