Danfoss VLT HVAC Drive FC 100 Series, Руководство по конструкции

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7.8.9 How to Control the Adjustable
Frequency Drive
This section describes codes which can be used in the
function and data fields of a Modbus RTU message.
7.8.10 Function Codes Supported by
Modbus RTU
Modbus RTU supports use of the following function codes
in the function field of a message.
Function Function Code
Read coils 1 hex
Read holding registers 3 hex
Write single coil 5 hex
Write single register 6 hex
Write multiple coils F hex
Write multiple registers 10 hex
Get comm. event counter B hex
Report slave ID 11 hex
Table 7.18
Function Function
Code Sub-
function
code Sub-function
Diagnostic
s 8 1 Restart communication
2 Return diagnostic register
10 Clear counters and
diagnostic register
11 Return bus message count
12 Return bus communication
error count
13 Return bus exception error
count
14 Return slave message count
Table 7.19
7.8.11 Modbus Exception Codes
For a full explanation of the structure of an exception code
response, please refer to ,
Function Field.
Modbus Exception Codes
Co
de Name Meaning
Modbus Exception Codes
1 Illegal
function The function code received in the query is
not an allowable action for the server (or
slave). This may be because the function
code is only applicable to newer devices
and was not implemented in the unit
selected. It could also indicate that the
server (or slave) is in the wrong state to
process a request of this type, for example
because it is not configured and is being
asked to return register values.
2 Illegal data
address The data address received in the query is
not an allowable address for the server (or
slave). More specifically, the combination of
reference number and transfer length is
invalid. For a controller with 100 registers, a
request with offset 96 and length 4 would
succeed, a request with offset 96 and length
5 will generate exception 02.
3 Illegal data
value A value contained in the query data field is
not an allowable value for server (or slave).
This indicates a fault in the structure of the
remainder of a complex request, such as
that the implied length is incorrect. It specif-
ically does NOT mean that a data item
submitted for storage in a register has a
value outside the expectation of the
application program, since the Modbus
protocol is unaware of the significance of
any particular value of any particular
register.
4 Slave device
failure An unrecoverable error occurred while the
server (or slave) was attempting to perform
the requested action.
Table 7.20
7.9 How to Access Parameters
7.9.1 Parameter Handling
The PNU (Parameter Number) is translated from the
register address contained in the Modbus read or write
message. The parameter number is translated to Modbus
as (10 x parameter number) DECIMAL.
7.9.2 Storage of Data
The Coil 65 decimal determines whether data written to
the Adjustable frequency drive are stored in EEPROM and
RAM (coil 65 = 1) or only in RAM (coil 65 = 0).
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