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Positioning
10.3.2 Data in the Data Block and in the Transfer Buffer
If the data interchange with the IP 240
•
is handled by standard function blocks, you must observe the contents of the data words in
the data block when writing and evaluating data.
•
is programmed as direct data interchange ( Chapter 11), you must observe the contents of
the data bytes in the transfer buffer when writing and reading data.
The permissible value ranges of the various items of data determine the number of bytes needed
to represent that item of data. Three "lengths" are possible, irrespective of whether the data is
forwarded in the data block or in the transfer buffer:
•
four bytes
•
two bytes
•
one byte
The table below shows the general layout of the data in the data block and in the transfer buffer.
When data is entered in the data block, entry begins with the nth data word. DL n identifies the
lefthand byte and DR n the righthand byte in data word "n".
The contents of the transfer buffer relate to the offset with which the byte is addressed. You can
obtain the complete address by adding the offset to the module start address (
"Direct Data Interchange").
•
4-byte data
Four bytes are provided for the following items of data:
- Position values for positions 1 to 254
- Distance values of ranges BEE1 to 3 for positions 1 to 254
- Position value for position 0
- Distance values of ranges BEE1 to 2 for position 0
- Range limit value for the rotary axis
- Zero offset
- Actual value
- Final value
Table 10-4. Layout of 4-Byte Data Items in the DB and in the Transfer Buffer
Data
block
DL
n
DR n
DL
n+1
DR n+1
Table 10-5. Numerical Representation of 4-Byte Data Items
Numerical
representation
Binary
BCD
without sign
with sign
10-12
Byte layout
Byte 1
Byte 2
Byte 3
Byte 4
Byte 1
Byte 2
23
16
SE
2
to 2
6
5
0
10
10
10
6
5
SG
10
10
10
Offset
in transfer buffer
0
1
2
3
Byte 3
Byte 4
15
8
7
2
to 2
2
4
3
2
1
10
10
10
4
3
2
1
10
10
10
IP 240
Chapter 11,
0
to 2
0
10
0
10
EWA 4NEB 811 6120-02a
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