Instruction manual

6. MODBUS COMMUNICATION PROTOCOL
IMR01H02-E3
54
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Data whose decimal point’s presence and/or position depends on input range
The position of the decimal point changes depending on the input range type because the Modbus
protocol does not recognize data with decimal points during communication.
The following data can have one of three decimal point positions:
• No decimal point
• One decimal place
• Two decimal place
For details, see 7. INPUT RANGE TABLES (P. 75).
Measured value (PV)
Set value monitor
Set value (SV)
Alarm 1 (Except the control loop break alarm)
Control loop break alarm (LBA)
Alarm 2 (Except the heater break alarm 1)
Alarm 3
Proportional band or heat-side proportional band
Overlap/deadband *
PV bias
* This item does not use in the MA901.
Example: When the temperature set value is -20.0 °C; -20.0 is processed as -200,
-200 = 0000H - 00C8H = FF38H
Set value (SV) High FFH
Low 38H
6.7.2 Data processing precautions
• Addresses in which data (holding register) is accessible are from 0000H to 02EEH and from 1388H
to 14A0H. If any address other than 0000H to 02EEH and 1388H to 14A0H is accessed, an error
response message returns. However, no error returns for any address from 03E8H to 0563H.
Therefore, do not access any of the above addresses.
• Read data of unused channel is 0.
• Any attempt to write to an unused channel is not processed as an error. Data can not be written into
an unused channel.
• If data range or address error occurs during data writing, the data written before error is in effect.
• Communication data includes data which becomes RO (read only) depending on the specification.
No error occurs even if data is written when set to RO. However in this case, no data is written.
For details, see 6.8 Communication Data List (P. 55).
• Send the next command message at time intervals of 30 bits after the master receives the response
message.