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.
UNACCEPTABLE DATA
Some programming is unacceptable since the NT935 AD does not provide for it; these data are discarded with no
EXCEPTION CODE.
CH 1-2-3: channels cannot be disabled
CH 1-2-3: FAN_2 cannot be enabled
CH 4: FAN_1 cannot be enabled
CH 4: FAN_INT cannot be enabled
CH 4: FAN_2 cannot be enabled if CH 4=no
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
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
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
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.
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