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PCA handling
The PCA portion of the PPO types 1, 2 and 5 will
handle a number of tasks. The master may control
and supervise parameters and request a response
from the slave, while the slave, apart from responding
to a request from the master may transmit a
spontaneous message.
Requests and responses is a handshake procedure
and cannot be batched, meaning that if the master
sends out a Read/write request, it has to wait for the
response, before it sends a new request. The request
or response data value will be limited to max. 4 bytes,
which implies that text strings are not transferable.
PCA - Parameter Characteristics
15 14 13 12
11
10 9 8 7 6 5 4 3 2 1 0
RC
SMP
RC:
Request/respons Characteristics
SPM: Toggle-Bit for Spontaneous Messages
PNU: Parameter #
Request/response handling
The RC portion of the PCA word defines the requests
that may be issued from the master to the slave as
well as what other portions of the PCV (IND and PVA)
are involved.
The PVA portion will transmit word-size parameter
values in bytes 7 and 8, while long word size values
require bytes 5 to 8 (32 bits).
If the Response / Request contains array elements,
the IND will carry the Array Subindex. If parameter
descriptions are involved, the IND will hold the Record
Subindex of the Parameter description.
RC content
Request
Function
0
No request
1
Request parameter value
2
Change parameter value (word)
3
Change parameter value (long word)
4
Request description element
5
Change description element
6
Request parameter value (array)
7
Change parameter value (array word)
8
Change parameter value (array long word)
9
Request number of array elements
10-15
Not used
MG.90.A2.02 – VLT is a registered Danfoss trademark
PNU
(Range: 0..15)
(Range: 1..1999)
FCM 300 PROFIBUS / VLT 2800 PROFIBUS
Response Function
0
No response
1
Transfer parameter value (word)
2
Transfer parameter value (long word)
3
Transfer description element
4
Transfer parameter value (array word)
5
Transfer parameter value (array long word)
6
Transfer number of array elements
7
Request rejected (incl. fault #, see below)
8
Not seviceable by PCV interface
9
Spontaneous message (word)
10
Spontaneous message (long word)
11
Spontaneous message (array word)
12
Spontaneous message (array long word)
13-15
Not used
If the slave rejects a request from the master, the RC word in
the PPO-read will indicate this by assuming the value 7.
The fault # will be carried by bytes 7 and 8 in the PVA element.
Fault #
Interpretation
0
Illegal PNU
1
Parameter value cannot be changed
2
Upper or lower limit exceeded
3
Subindex corrupted
4
No array
5
Data type false
6
Cannot be set by user (reset only)
7
Description element cannot be changed
8
IR required PPO-write not available
9
Description data not available
10
Access group
11
No parameter write access
12
Key word missing
13
Text in cyclical transmission not readable
14
Name in cyclical transmission not readable
15
Text array not available
16
PPO-write missing
17
Request temporarily rejected
18
Other fault
19
Date in cyclical transmission not readable
130
There is no bus access to the parameter
called
131
Data change is not possible because
factory Setup has been selected
17
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