Model FL3102
31
7.5.1 Exception Responses
Byte
MODBUS
Range
Referenced to FL3102
1
st
Slave Address
1-247* (Decimal) FL3102 ID (Address)
2
nd
Function Code
83 or 86 (Hex)
MSB is set with Function Code
3
rd
Exception Code 01 - 06 (Hex)
Appropriate Exception Code (See
below)
4
th
CRC Lo
00-FF (Hex)
CRC Lo Byte
5
th
CRC Hi
00-FF (Hex)
CRC Hi Byte
Figure 38 Exception Responses
7.5.1.1 Function Code Field
In a normal response, the FL3102 echoes the function code of the
original query in the function code field of the response. All the Function
Codes have a most-significant bit (MSB). In an exception response, the
FL3102 sets the MSB of the function code to a one (1). With the function
code’s MSB set, the master can recognize the exception response and
can process the data field for the exception code from the FL3102
response message.
7.5.1.2 Exception Code Field
In a normal response, the FL3102 returns data and status in the data
field, which was requested in the query from the master. In an exception
response, the FL3102 returns an exception code in the data field, which
describes the FL3102 condition that caused the exception. Below is a list
of exception codes that are supported by the FL3102:
Code
Name
Description
01
Illegal Function
The function code received in the query is not an
allowable action for the FL3102.
02
Illegal Data Address
The data address received in the query is not an
allowable address for the FL3102.
03
Illegal Data Value
A value contained in the query data field is not an
allowable value for the FL3102.
04
Slave Device Failure
An unrecoverable error occurred while the FL3102
was attempting to perform the requested action.
05
Acknowledge
The FL3102 has accepted the request and is
processing it, but a long duration of time will be
required to do so. This response is returned to
prevent a timeout error from occurring in the
master.
06
Device Busy
The FL3102 is engaged in processing a long-
duration program command. The master should
retransmit the message later when the slave is
free.
Figure 39 Exception Code Field