10/05 AWB8230-1541GB
The network protocol
153
Structure of response
Required transfer time
• The time between receiving a request from the master and the
frequency inverter’s response consists of the rest time (3.5
characters) and PNU C078 (the waiting time to the fault
message).
• Once the master has received a response from the frequency
inverter, it must wait for at least the rest time before it can send
a new request.
Normal response
• If the master’s request contains the loopback function (08
hex
),
the frequency inverter returns the same content.
• If the request contains a write register function (05
hex
, 06
hex
,
0F
hex
or 10
hex
), the frequency inverter returns the request as its
response.
• If the request contains a read register function (01
hex
, hex or
03
hex
), the frequency inverter returns the read data with the
slave address and function code as its response.
Response in fault condition
If the request contains an error (except for a transmission error),
the frequency inverter responds with an exception message and
does not perform an action.
The exception message can be evaluated in the user program. It
consists of the sum of the enquiry’s function code and code 80
hex
.
Structure of exception message:
• Address (slave)
• Function code
•Error code
•CRC-16
No response
In the following cases, the frequency inverter ignores the request
and does not send a reply:
• On receiving a broadcast request
• If the request contains a transmission error
• If the slave address in the request does not match the inverter’s
address
• If the time interval between the data blocks is less than 3.5
characters
• If the data length is invalid
Exception
code
Description
hex
01 The function is not supported.
02
The specified address does not exist or was not found.
03 The data format is not supported or is wrong.
21 The number of the holding registers is too large or the
data is outside the frequency inverter’s range.
22 • The function for changing register contents can not
be used during frequency inverter operation.
• The function sends an ENTER signal during
operation
• The function writes to the register during operation
• The function writes to read-only register or coil
h
The master must be programmed to repeat the request if
it does not receive a response within a specified time.
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