Date Code 980420
General Description
2-5
SEL-2711 Instruction Manual
Table 2.1: Modbus Data Access Commands
Function Code (Decimal)
Command Name
1**
Read Discrete Output Status (0xxxx)
2
Read Discrete Input Status (1xxxx)
3**
Read Output Register (4xxxx)
4**
Read Input Register (3xxxx)
5**
Force Single Coil (0xxxx)
6
Preset Single Register (4xxxx)
7
Read Exception Status
8*
Get/Clear Network Statistics (Subfunction 21)
15
Force Multiple Coils (0xxxx)
16
Preset Multiple Registers (4xxxx)
17
Report Slave ID
*
Use only subfunction 21 of function 8 for Modbus Plus networking data.
**
These function codes are supported by the SEL-2711
Modbus Data Addressing
Modbus Plus addresses typically have the following ranges:
Coils (Output Status)
1
-
9999
Input Status
10001
-
19999
Input Registers
30001
-
39999
Holding (Output) Registers
40001
-
49999
These address ranges imply what function codes can be used on the data. For instance, holding
registers can be accessed using function codes 3, 6, and 16 (see Table 2.1).
The actual addresses passed in the Modbus Plus messages start at 0. For example, for holding
registers, the address within the message is 40001 less than what is viewed by the user.
See
Appendix C: Modbus Plus Message Example
to see how an actual Modbus Plus message is
structured.
P
RODUCT
O
VERVIEW
The SEL-2711 allows a remote Modbus Plus device to read meter, demand meter, target, and
history information available from the host system. It also allows User Region data to be read.
The SEL-2711 can be configured to send user-configurable Modbus Plus global data. The
SEL-2711 captures all Modbus Plus global data from the network and stores it to a data region so
it is available to the host system. The SEL-2711 accepts control operations; the host system
