Emerson SI-DeviceNet, Руководство пользователя

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32
SI-DeviceNet User Guide
Issue Number: 2
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.
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
Cyclic data alignment
S.01.014
Default 32 (0)
Range 32 (0) or 16 (1) bits
Access RW
Parameter
size
(bits)
Actual data size (bits)
Alignment = 16 bits
Actual data size (bits)
Alignment = 32 bits
1
16
32
8
16
32
32
Data channel
Data words
used
Mapping
for slot 3
Setting
Data
width
(bits)
Mapping status
IN channel 1 IN word 0, 1 Pr 3.02.001 0.10.040 16 Pr 10.040 , status word
IN channel 2 IN word 2, 3 Pr 3.02.002 0.02.001 32
Pr 02.001 , post-ramp speed
reference
IN channel 3 IN word 4, 5 Pr 3.02.003 0.04.020 16
Pr 04.020 , Motor load as % of
rated motor load
IN channel 4 IN word 6, 7 Pr 3.02.004 0.14.021 16 Pr 14.021 , PID1 feedback
IN channel 5 IN word 8, 9 Pr 3.02.005 0.14.001 16 Pr 14.001 , PID1 output
OUT channel 1 OUT word 0, 1 Pr 3.03.001 0.06.042 16 Pr 06.042 , control word
OUT channel 2 OUT word 2, 3 Pr 3.03.002 0.01.021 32 Pr 01.021 , preset reference 1
OUT channel 3 OUT word 4, 5 Pr 3.03.003 0.02.011 32 Pr 02.011 , acceleration rate 1
OUT channel 4 OUT word 6, 7 Pr 3.03.004 0.02.021 32 Pr 02.021 , deceleration rate 1
OUT channel 5 OUT word 8, 9 Pr 3.03.005 0.14.020 16 Pr 14.020 , PID1 reference