Function Codes - ABB FSCA-01 Manual

36

Function codes

The FSCA-01 RS-485 Adapter Module supports the Modbus
function codes shown below.
Function code
Communication
Name
03h Read Holding Registers
06h Write Single Register
08h Diagnostics
10h Write Multiple Registers
17h Read/Write Multiple
Registers
Description
Reads the contents of a contiguous block of
holding registers in a server device.
Writes a single holding register in a server
device.
Provides a series of tests for checking the
communication between the master and the
slave devices, or for checking various internal
error conditions within the slave.
The following subcodes are supported:
00 Return Query Data:
The data passed in the request data field is to
be returned in the response. The entire
response message should be identical to the
request.
01 Restart Communications Option:
The serial line port of the slave device must be
initialized and restarted, and all of its
communication event counters cleared. If the
port is in the Listen Only mode, no response is
returned. If the port is not in the Listen Only
mode, a normal response is returned before the
restart.
04 Force Listen Only Mode:
Forces the addressed slave device to the Listen
Only mode. This isolates it from the other
devices on the network, allowing them to
continue communicating without interruption
from the addressed remote device. No response
is returned. The only function that will be
processed after this mode is entered is the
Restart Communications Option function
(subcode 01).
Writes the contents of a contiguous block of
holding registers in a server device.
Writes the contents of a contiguous block of
holding registers in a server device, then reads
the contents of a contiguous block of holding
registers (same or different than those written)
in a server device.