RKC INSTRUMENT Z-TIO-G, Instruction Manual, Page: 76 / 246

7. MODBUS
7-12
IMS01T28-E4
7.3 Data Processing Precautions

The numeric range of data used in Modbus protocol is 0000H to FFFFH. Only the set value within the
setting range is effective.
FFFFH represents

1.

The Modbus protocol does not recognize data with decimal points during communication.
Example1: When Output limiter high set value is 85.0 %, 85.0 is processed as 850,
850 = 0352H
Output limiter high High 03H
Low 52H
Example2: When Set value (SV) is

20.0

C,

20.0 is processed as

200,

200 = 0000H

00C8H

FF38H
Set value (SV) High FFH
Low 38H

In this communication, the variables that memory area includes handles different address with for
Control area and for setting area.

If data (holding register) exceeding the accessible address range is accessed, an error response message is
returned.

Read data of unused item is a default value.

Any attempt to write to an unused item is not processed as an error. Data cannot be written into an
unused item.

If an error (data range error or address error) is detected in the data writing process, an error is returned.
Writing is aborted at and after the addresses where an error occurred. After having completed the setting,
check to see if the data was properly written.

An attribute of the item for functions which are not in the controller is RO (read only). If read action to
this item is performed, the read data will be “0.” If write action to this item is performed, no error
message is indicated and no data is written.
For details, refer to 8. COMMUNICATION DATA LIST (P. 8-1) .

Commands should be sent at time intervals of 24 bits after the master receives the response message.