Instruction manual

7. MODBUS
IMS01J02-E1
123
7.3.2 Data processing precautions
 With Modbus protocol, the maximum number of channels per slave address is 20.
 The accessible data (holding register) address range is from 0000H to 1FFFH.
If data exceeding the 1FFFH is accessed, an error response message is returned.
 Do not write data to any address which is not described in a list of data maps.
 Initialize the module after changing to stop the control.
 Read data of unused channel and undefined address 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.
 Some communication data may become invalid depending on the module selection or the
configuration of the SR Mini HG SYSTEM control unit.
If any one of the conditions listed below occurs and data items written are within the setting range,
read data becomes “0.” Under these conditions, no error response message will occur.
− When heat/cool control, manual output value and auto/manual transfer are invalid.
− When heat control, cool-side manipulated output, cool-side proportional band, overlap/deadband
and cool-side proportioning cycle time are invalid.
− When ON/OFF control, cool-side manipulated output, heat-side and cool-side proportional band,
integral time, derivative time, overlap/deadband and cool-side proportioning cycle time are
invalid.
− When current/voltage output , heat-side and cool-side proportioning cycle time are invalid.
− When only the heater break alarm function is provided, current transformer input measured
value ,
current transformer input measured value 2, heater break alarm status, heater break alarm set
value 1 and heater break alarm set value 2 are valid.
− When only the control loop break alarm (LBA) function is provided, control loop break alarm
(LBA) status, use selection, time and deadband are valid.