NORD Drivesystems BU0090 - Manual (Page 44)

NORDAC AS-Interface Manual
44 BU 0090 GB
5.3 Read / Write parameter string
(read from slave / write to slave)
The parameterisation of the frequency inverter can be carried out and checked with the commands Read
parameter string
and Write parameter string. Information parameters can also be read out in the same way.
For both reading and writing, the first two bytes in the parameter string are used as an index. Then the data
content is transferred. The number of data words is restricted to 8 words (16 Byte). The total string transfer
length is therefore limited to a maximum of 9 words (18 Bytes). Transfer is always in the form of complete
words, i.e. odd numbers of bytes may not be transferred. There is a facility for simply accessing several
parameters (direct parameters), and a more complex access to all parameters via the USS protocol. Both
parameterisation facilities are described in the following sections.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Index Data Data Data Data Data Data Data Data
Byte Contents
0+1 :
Index
2 – 17 : data (length varies according to content, but always in the form of words (2 bytes) and with the
high-byte first)
Index (2 Byte) Data content Data length
0000
hex
– 0001
hex
Reserved -
0002
hex
PKW-Parameter-String (USS protocol) (see Section 5.3.2) 6 Byte or 8 Byte
0003
hex
– 003F
hex
Reserved -
0040
hex
– 00A5
hex
Direct parameter (see Section 5.3.1) 2 bytes each. A maximum of 16
bytes can be transferred
00A6
hex
– FFFF
hex
Reserved -
Reserved indices may not be set, as this can alter the behaviour of the system.
5.3.1 Direct parameters
The list of direct parameters contains selected parameters from the entire parameter range of the frequency
inverter. With direct parameters, individual or several parameter sets or array elements can be written
simultaneously (from 1 to 8 words or values). In order to read a direct parameter, the index of the relevant
direct parameter must be sent with a Write order of length 1 word prior to the read command. After this, the
index and the associated value (total 2 words) are transferred with a Read command.
Even after a Write order in which one or more values are written, with the next Read command the first value is
read back. Here a certain time (
≈ 200ms) must elapse before the value can be checked with a Read command
(very important for the transfer of several parameters). After each Read command the index is automatically
increased by 1 and the next value can be read without starting a further Write order. After reading the last
direct parameter the index is again set to the first direct parameter.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Index Array-
element 1
Array-
element 2 Array-
element 3 Array-
element 4 Array-
element 5 Array-
element 6 Array-
element 7 Array-
element 8
Index Parameter
set 1
Parameter
set 2 Parameter
set 3 Parameter
set 4
As up to 8 data words (16 Byte) can be transmitted, it is also possible to transfer up to 4 parameter sets from
two consecutive parameters by means of a single direct parameter Write command. If e.g. for SK 700E the
index 0054
hex
and 8 data words are written, the 4 parameters of the start-up time P102 and the braking time
P103 are each changed. If only two parameter sets are available (SK 300E) the data words for the parameter
sets 3 and 4 are not processed, i.e. the two data words are simply placeholders.