Uss Read Request - Siemens SINAMICS G120 CU230P-2 HVAC Operating Instructions Manual

Configuring the fieldbus
6.2 Communication via RS485
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:
● Parameter number without offset: Bits 10 ... 0 in the PKE word:
● Offset of the parameter number in the byte page index of the word IND:
● Index of the parameter in the byte subindex of the word IND:
● Because you want to read the parameter value, words 3 and 4 in the parameter channel
Table 6- 25 Request to read parameter r2122[2]
PKE (1st word)
AK PNU
15 ... 12 11 10 ... 0
0x6 0 0x7A
(dec: 122)
128
Request identifier = 6
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
for this example: When offset = 2000, this corresponds to a page index value of 0x80
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) .
for requesting the parameter value are irrelevant. They should be assigned a value of 0,
for example.
IND (2nd word)
Page index Subindex
(H byte)
15 ... 8
0x80
Frequency inverters with Control Units CU230P-2 HVAC, CU230P-2 DP, CU230P-2 CAN
PWE1(H word)
(L byte)
7 ... 0 15 ... 0
0x02 0x0000
Operating Instructions, 01/2011, FW 4.4, A5E02430659B AD
PWE (3rd and 4th words)
PWE2(L word)
Drive
Object
15 ... 10
0x0000
9 ... 0
0x0000