SOH = 0x01
STX = 0x02
ETX = 0x03
EOT = 0x04

LIMIT_BYTE_COUNT = 255

CACHE_REFRESH_DELAY = 5 * 60 

function readRegister (reg, device, unitId)
    
   local iAddrString= tostring(reg.internalAddr)
   local targetBase = tonumber(string.sub(iAddrString, 1, (#iAddrString - 1)))
   local targetOffset = tonumber(string.sub(iAddrString, -1))
   
   if replies[targetBase] then 
       ERROR('there is entry for targetBase!')
       local ifData = replies[targetBase][targetOffset]
       if ifData then 
            ERROR('there is an entry for page: ')
            tprint(ifData) 
            return ifData['data']
       end 
        
   end 
   
   
--   ERROR('Target base and offsets ' .. targetBase .. ' ' .. targetOffset)
   
   if syncRequest() then 
       local packet = finishRequest()
       
       if packet then 
           local b, o = parseRequest(packet)
           b = tonumber(b) ; o = tonumber(o)
           
           if (b and o) then 
               if (not readUntil(string.byte('#'))) then 
                  return false 
               else 
                  
                  local replyAddr = tonumber(readString(4))
                  
                  if (replyAddr == b) then 
                        
                        ERROR('reply address equals requst addr = ' .. replyAddr)
                     local data = readUntil(ETX) 

                                                -- DATA PROCESSING 
                     if not data then  
                         ERROR('Could not read data in response ((( ') 
                         return false 
                     else                      
                         
                            -- get string presentation 
                         local dataAsString = {}
                             for i, v in ipairs(data) do 
                                dataAsString[i] = string.char(v) 
                             end 
                         data = table.concat(dataAsString) 
                        --  ERROR(data)  
                            
                            -- check if data in cache 
                         if (not replies[b]) then 
                             replies[b] = {} ;      ERROR('Entry for the ' .. b .. 'device was created!')-- create entry for DEVICE 
                         end 
                            -- if sub-set in the group 
                         if (not replies[b][o]) then 
                             replies[b][o] = {} 
                             replies[b][o]['data'] = data ; ERROR('Entry for the data in ' .. b .. ' ' .. o ..  'was created!')-- create entry for data 
                             replies[b][o]['stamp'] = now 
                             
                             ERROR('Now data in cache = ' .. replies[b][o]['data']) 
                         end      
                          -- check if data is old or no 
                         if ((now - replies[b][o]['stamp']) > CACHE_REFRESH_DELAY) then 
                             replies[b][o] = nil          ; ERROR("Killed data in " .. b .. ' ' .. o ..  'after timeout!')
                         end 
                         
                         
                         ERROR('types of targetBase, targetOffset, b, o')
                         ERROR(type(targetBase) .. ' ' .. type(targetOffset) .. ' ' .. type(b) .. ' ' .. type(o))
                         ERROR('data in cache in this point ' .. replies[b][o]['data']) 
                         
                         if not replies[targetBase] or not replies[targetOffset] then 
                             ERROR('No data in cache for ' ..  targetBase .. ' '  .. targetOffset)     
                             return false 
                         else 
                             return replies[targetBase][targetOffset]['data']
                         end 
                         return 1 
                      end 
                  else 
                      ERROR('reply address does not equal requst addr = ' .. replyAddr .. ' ' .. b)
                      return false         
                  end 
               end 
           
           else 
               ERROR('Wrong base offset from parseRequest!')
               return false 
           end 
       else 
           return false 
       end 
   else 
       return false 
   end 
   
end -- readRegister