Configuring the fieldbus
6.2 Communication via RS485
Frequency inverters with Control Units CU230P-2 HVAC, CU230P-2 DP, CU230P-2 CAN
128
Operating Instructions, 01/2011, FW 4.4, A5E02430659B AD
6.2.2.6
USS read request
Example: Reading out alarm messages from the inverter.
The parameter channel comprises four words (p2023 = 4). In order to obtain the values of
the indexed parameter r2122, you must fill the telegram of the parameter channel with the
following data:
●
Request parameter value (field): Bits 15 … 12 in the PKE word:
Request identifier = 6
●
Parameter number without offset: Bits 10 … 0 in the PKE word:
Because you can only code parameter numbers from 1 … 1999 in the PKE, you must
deduct as large an offset as possible, a number divisible by 2000, from the parameter
number, and transfer the result of this calculation to the PKE word.
In our example, this means: 2122 - 2000 = 122 = 7AH
●
Offset of the parameter number in the byte page index of the word IND:
for this example: When offset = 2000, this corresponds to a page index value of 0x80
●
Index of the parameter in the byte subindex of the word IND:
If you wish to read-out the last alarm, then you must enter index 0, for the third from last,
index 2 (example). You can find a detailed description on the history of the alarm
messages in the Section Alarms (Page 288) .
●
Because you want to read the parameter value, words 3 and 4 in the parameter channel
for requesting the parameter value are irrelevant. They should be assigned a value of 0,
for example.
Table 6- 25 Request to read parameter r2122[2]
PKE (1st word)
IND (2nd word)
PWE (3rd and 4th words)
PWE2(L word)
AK
PNU
Page index
(H byte)
Subindex
(L byte)
PWE1(H word)
Drive
Object
15 … 12 11
10 … 0
15 … 8
7 … 0
15 … 0
15 … 10
9 … 0
0x6
0
0x7A
(dec: 122)
0x80
0x02
0x0000
0x0000
0x0000
Summary of Contents for SINAMICS G120 CU230P-2
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