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Communication System Manual
3.4.4 Examples of (acyclic) message requests:
1 and 2
3
Parameter
Parameter
identifier
subindex
Fig. 10: (Acyclic) message address
Example 1: Message request: Write a parameterizable value
The "z" release setting current is to be set to a value of 25000 A. The message address is therefore
782, 5, 0, 22, 0 in accordance with page 48. Bytes (= octets) 1 and 2 must also contain the request
identifier for write and parameter number 782. The detailed structure of octets 1 and 2 can be seen in
Fig. 11, page 54.
Byte (octet) 1
15
14
13
12
Request identifier
Example 1:
0
0
1
1
Fig. 11: Structure of parameter identifier (bytes 1 and 2)
The request identifier for read is "1", for write "3": The request identifier must be entered in bits 15 -
12 of byte 1 as illustrated in Fig. 11, page 54, in this case a "1" in bits 13 and 12. Bits 14 and 15 both
equal 0. The parameter number must then be entered in bits 0 - 10, in the above example the binary
value "01100001110". Similarly the binary values "00000101" (= 5), "00000000" (= 0), "00010110" (= 22)
and "00000000" (= 0) must be entered in bytes 3, 4, 5 and 6 respectively. Finally, the binary code for
25000 (the setting current), i.e. "0110000111101000", must be written in bytes 7 and 8.
Example 2: Message request: Read a read-write value
Message address 782, 5, 0, 22, 0, is also used to read the "z" release setting current. The same values
as in example 1 are written in bytes 1 to 6 here (with the exception of the request identifier). Because this
is a read request, the request identifier = 1 and bits 15 to 12 contain the binary value "1" (0001). No
entries are necessary in bytes 7 and 8. These bytes will be used to store the read value of the "z" release
setting current.
Example 3: Message request: Read a read-only value
The procedure for reading read-only values (e.g. operational data) is the same as for read-write values,
i.e. the request identifier and the listed message address are written to bytes 1, 2, ... of the PLC I/O area
of 3WN6. If, for example, the circuit-breaker state (T-Nr. 1:1) is to be read, then the request identifier
must be set to 1 (byte 1), the value "741" must be entered in bytes 1 and 2, the value "1" in byte 3 and
the value "0" in byte 4. These values must be entered in binary code. The read value for circuit-breaker
state is stored in bytes 5, 6, 7 and 8.
Important notice: Only the cyclic data from the 3WN6 circuit-breaker (see pages 52 ff.) are regularly
updated in the PLC I/O area. Acyclic data are read on request only. If, for example, byte (octet) 9 of the
I/O area contains a "group fault signal" (bit 8 = 1), then the "Tripped signals" (and possibly the "fault
signals" in the case of releases N and P with Z=F05) will need to be read for a more detailed fault
analysis.
54
Byte (Octet)
4
5 (= OS1)
Parameter value (integer data value)
Parameter identifier
Bit number
11
10
9
8
-
-
0
1
1
© Copyright Siemens AG 1998. All rights reserved.
6 (= OS2)
7 (= OS3)
Byte (octet) 2
7
6
5
4
Parameter number
0
0
0
0
3WN6 Circuit-Breakers
8 (= OS4)
3
2
1
0
1
1
1
0
Version 1.0 (05/98)
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