Rockwell Automation 1771-DCM USER MANUAL 1771-DCM User Manual
Page 44
Calculating Transfer Time
Chapter 7
7Ć10
Figure 7.2
Nominal Time Table
1
2
3
4
1
45 50 60 65
2
70 70 75
3
85 95
4
100
Time (ms)
Active I/O channels
containing one or more
blockĆtransfer modules
Number of Active I/O Channels
Step 2 Ć Determine a time from the table. Example values have been added for a BTW instruction.
Number of active I/O channels: 3
Number of active I/O channels containing one or
more blockĆtransfer module: 2
Time from table: 70 ms
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3. Compute the approximate transfer time for each block transfer I/O
channel. Use values from your channel diagram (Figure 7.1), a value
from the table (Figure 7.2), and the formula from Step 6 above. We
make these calculations for you in Figure 7.3.
Figure 7.3
Computing Channel Times
CT4 = Not an Active Channel
CT = Channel Time
CT2 = Not a Block Transfer Channel
CT1 = [ 70 ms ] x [ 3 ] + [ 4Ć1 ] x 9 ms
210 ms + 3 x 9 ms
237 ms
CT3 = [ 70 ms ] x [ 1 ] + [ 2Ć1 ] x 9 ms
70 ms + 9 ms
79 ms
CT =
Nominal
Time
x
# BT Modules
on BT Channel
+
I/O Chassis
on BT Channel
x 9 ms
STEP 3:
Compute the scanner time for each block transfer channel.
Example values have been added.
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