Rockwell Automation 1771-DCM USER MANUAL 1771-DCM User Manual
Page 41
Calculating Transfer Time
Chapter 7
7Ć7
Scanner Scan
The time required for the scanner to complete a read or write block
transfer depends on the number of other block transfer modules on the
same scanner channel that are enabled simultaneously. Use the following
procedure to calculate the time required for the PLC-3 processor to
perform all block transfers on the channel.
1.
Determine the number of active I/O channels on the scanner.
2.
Determine the number of I/O channels with block transfer modules.
3.
Use these tables to determine the nominal block transfer time using
the numbers from Steps 1 and 2.
Nominal Block Transfer Times (ms) for a BTW
Channels with
Block Transfer Modules
1 Active
Channel
2 Active
Channels
3 Active
Channels
4 Active
Channels
1
45
50
60
65
2
ĆĆ
70
70
75
3
ĆĆ
ĆĆ
85
95
4
ĆĆ
ĆĆ
ĆĆ
100
Nominal Block Transfer Times (ms) for a BTR
Channels with
Block Transfer Modules
1 Active
Channel
2 Active
Channels
3 Active
Channels
4 Active
Channels
1
35
50
50
60
2
ĆĆ
60
60
65
3
ĆĆ
ĆĆ
70
80
4
ĆĆ
ĆĆ
ĆĆ
90
Block transfer times typically are similar regardless of the type of block
transfer module or the number of words transferred. Nominal read block
transfer times typically are faster than nominal write block transfer times
by approximately 10 ms. In this example, consider them the same.