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Cyclic data alignment
S.01.014
By default, the SI-DeviceNet uses 32 bits for each data channel, even if the target
parameter in the drive is a 16-bit parameter. This strategy (known as casting), ensures
that the cyclic data transmitted over the DeviceNet network remains aligned with the
memory locations in 32-bit PLC's. When cyclic data alignment (Pr S.01.014) is set to "16
bits", a data channel will only use 32 bits if the target drive parameter is a 32-bit
parameter. If the target drive parameter is only 1, 8 or 16 bits wide, 16 bits will be used
for that particular data channel as shown in the following table.
Parameter
size
(bits)
1
8
16
32
The following examples demonstrate setting up a network using five cyclic channels for
both IN and OUT data with the cyclic data alignment first set to 32 bits and then set to
16 bits.
Table 6.3 shows the mapping parameters where five IN and five OUT cyclic data
channels are required. With data alignment set to 32 bits, each data channel uses 32
bits (two data words, so a total of ten words are required).
Table 6.3 Mapping parameters
Data channel
IN channel 1
IN channel 2
IN channel 3
IN channel 4
IN channel 5
OUT channel 1 OUT word 0, 1
OUT channel 2 OUT word 2, 3
OUT channel 3 OUT word 4, 5
OUT channel 4 OUT word 6, 7
OUT channel 5 OUT word 8, 9
32
Default
32 (0)
Range
32 (0) or 16 (1) bits
Access
RW
Actual data size (bits)
Alignment = 16 bits
16
32
Data words
Mapping
used
for slot 3
IN word 0, 1
Pr 3.02.001
IN word 2, 3
Pr 3.02.002
IN word 4, 5
Pr 3.02.003
IN word 6, 7
Pr 3.02.004
IN word 8, 9
Pr 3.02.005
Pr 3.03.001
Pr 3.03.002
Pr 3.03.003
Pr 3.03.004
Pr 3.03.005
Actual data size (bits)
Alignment = 32 bits
Data
Setting
width
(bits)
0.10.040
16
Pr 10.040, status word
Pr 02.001, post-ramp speed
0.02.001
32
reference
Pr 04.020, Motor load as % of
0.04.020
16
rated motor load
0.14.021
16
Pr 14.021, PID1 feedback
0.14.001
16
Pr 14.001, PID1 output
0.06.042
16
Pr 06.042, control word
0.01.021
32
Pr 01.021, preset reference 1
0.02.011
32
Pr 02.011, acceleration rate 1
0.02.021
32
Pr 02.021, deceleration rate 1
0.14.020
16
Pr 14.020, PID1 reference
SI-DeviceNet User Guide
32
Mapping status
Issue Number: 2
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