WF-2000 Series AIO
User’s Manual (Ver. 1.2, May./2014) ------------- 46
Table
5-2 Supports Function Codes of WF-2000 series
Function Code
Descriptions
01 (0x01)
Read Coil Status
02 (0x02)
Read Input Status
03 (0x03)
Read Holding Registers
04 (0x04)
Read Input Registers
05 (0x05)
Force Single Coil
15 (0x0F)
Force Multiple Coils
16 (0x10)
Preset Multiple Registers
Any other function code request will be returned with an error
response indicating the function code is not supported, as well as a
request for too much data or data at a register address that not present.
5.2.3
Data
The data field of Modbus request sent from a client to server devices
contains additional information that the server uses to take the action
defined by the function code. This can include items like discrete and
register addresses, the quantity of items to be handled, and the count of
actual data bytes in the field.
The data field may be nonexistent (of zero length) in certain kinds of
requests; in this case the server does not require any additional
information. The function code alone specifies the action.
5.2.4
Response
If no error occurs related to the Modbus function requested in a
properly received Modbus PDU (Protocol Data Unit) the data field of a
Modbus response from a server to a client contains the data requested.
If an error related to the Modbus function requested occurs, the field
contains an exception code that the server application can use to
determine the next action to be taken.
