Beijer Electronics NA-9379 - Manual (Page 82)

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MODBUS Programmable I/O NA-9379 FnIO S-Series
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A.6 Error Response
In an exception response, the server sets the MSB of the function code to 1. This makes the function code value in
an exception response exactly 80 hexadecimal higher than the value would be for a normal response.
• Exception Response Example
Field name Example RTU ASCII ASCII (bus line)
Start of Frame - t1-t2-t3
“,”
0x3A
Slave Address 0x07 0x07 “07” 0x30, 0x37
Function Code 0x81 0x81
“81”
0x38, 0x31
Exception Code 0x02 0x02
“02”
0x30, 0x32
Error Check (CRC/LRC) - 0x22, 0xC0 “76” 0x37, 0x36
End of Frame - t1-t2-t3 CR, LF 0x0D, 0xA
• Exception Codes
Exception
Code
Name Description
01 Illegal Function The function code received in the query is not an allowable action
for the server (or slave).
02 Illegal Data Address The data address received in the query is not an allowable address
for the server (or slave).
03 Illegal Data Value A value contained in the query data field is not an allowable value
for server (or slave).
04 Slave Device Failure An unrecoverable error occurred while the server (or slave) was
attempting to perform the requested action.
05 Acknowledge The server (or slave) has accepted the request and is processing it,
but a long duration of time will be required to do so.
06 Slave Device Busy Specialized use in conjunction with programming commands.
The server (or slave) is engaged in processing a long–duration
program command. The client (or master) should retransmit the
message later when the server (or slave) is free.
08 Memory Parity Error The server (or slave) attempted to read record file, but detected a
parity error in the memory. The client (or master) can retry the
request, but service may be required on the server (or slave)
device.
0A Gateway Path Unavailable Specialized use in conjunction with gateways, indicates that the
gateway was unable to allocate an internal communication path
from the input port to the output port for processing the request.
- NA-9171, NA-9173 response exception code 01, 02, 03, 04 and 06.