Serial interface (Modbus)
10/05 AWB8230-1541GB
160
Exception signal (error code)
In the Modbus protocol only the master manages the data
exchange. It addresses each slave separately and waits for a
response (except in broadcasting, in which it does not wait for a
reply).
If the slave does not respond within a specified time (the latency),
the master declares it not present. If a transmission error occurs,
the master repeats the request.
If a slave receives an incomplete message it sends an exception
message to the master. The master then decides whether it
resends the data or not.
The exception message contains the following fields:
• Address (slave)
• Function code
•Error code
•CRC-16
The function code of the exception message is formed by adding
80
hex
to the request’s function code.
The error code describes the reason for the exception response:
Saving new register data (ENTER function)
The data transmitted to the frequency inverter with function
“Force single register” or “Force multiple registers” (06
hex
, 10
hex
)
is initially saved only in temporary memory. If the frequency
inverter is switched off (POWER = Off), this data is lost. After a
restart, the frequency inverter would then load the previously
saved data data.
With the ENTER function, the new data is saved permanently.
Sending the ENTER command
Write the selected data to holding register 0901
hex
with function
“Force single register” (06
hex
).
Function code
Request Exception response
hex hex
01 11
03 13
05 15
06
16
0F 1F
10
90
Error code
Description
hex
01 The function is not supported.
02 The address was not found.
03 The data format is not permissible or is incorrect.
21 The number of the holding register is too high.
22 The register’s content must not be changed
while the frequency inverter is in RUN mode:
• The function sends an ENTER command
during operation.
• The function writes to the register during
operation
• The function writes to read-only register or
coils
h
The ENTER function requires a long time. You can query
its status with the “Force data” coil (001A
hex
).
The frequency inverter’s memory has a limited service life
(about 100000 write cycles). Frequent use of the ENTER
function reduces its lifespan.
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