ERROR CODES (exception codes) 
 
In case of a wrong request, ModBus will answer with modified codes and codified errors according to the following: 
 
1:   - Unsupported function code 
2:   - Wrong data address 
3:   - Wrong data (for instance length) 
 
 
The memory area containing the HFN datum must undergo no forcing. 
 
In the case in which all the fans are turned off (F1, F2) the test of the relay will not take place. 
 
 
 
ILLEGAL DATA  
 
On the other hand, some combinations are programming errors because they are wrong settings; in this case the error 
code is ILLEGAL_DATA. This information is accessible to ModBus by reading the register 7. 
 
 
NO ERROR             
CH_1     Trip ≤ Alarm 
CH_4     Trip ≤ Alarm 
FAN_1    ON ≤ OFF 0 FAN INT ≤ 10 
FAN_2    ON ≤ OFF 
No channel enabled 
Value  HFN > max        see table: SYSTEM - Setting and Status 
Value  FCD > max        see table: SYSTEM - Setting and Status 
Value  4.20 > max        see table: SYSTEM - Setting and Status 
Value  Voting  > max    see table: SYSTEM - Setting and Status 
 
Note. If the value of Voting is higher than the max value expected for the model in question, it will be set equal to "0", that is 
NO_VOTING. 
 
 
GENERAL UNIT NOTE  
 
The models of the unit can be equipped with different options ; to avoid disruption of production , their existence is defined 
by Fw indicated power , with messages dedicated on display LEDs . 
 
This information can be accessed by reading the Modbus register 6 ( option ) with the following meaning : 
LOW Byte 
 
               Bit_0     = AD: 4.20mA + Modbus RS485  
 
HIGH Byte  
               Bit_0/1  = 00 - Range 0°C - 240°C 
               Bit_0/1  = 10 - Range -40°C ÷ +200°C 
               Bit_4/7  = 0000  sensor Pt100 
 
In case of Ethernet option Modbus and 4.20mA mode shall not be active on the display. They will be readable from the log. 
 
Note: in case the values programmed from ModBus are out of range, it will generate a "exception" error response 
to date. 
 
 
POLLING FREQUENCY  
 
We recommend polling frequencies equal to or greater than 1 second are adopted.  
More frequent polling can overload the system without any benefit whatsoever. In multi-device RS485 lines, interrogated in 
sequence,  it  may  be  useful  to  enter  a  delay  between  polls  in  relation  to:  the  number  of  connected  devices,  the 
communication speed and the number of read registers.