Rockwell Automation 2711 PANELBUILDER SOFTWARE USER MANUAL - Manual (Page 384)

PLC Programming Considerations
Appendix A
A-20
PLCĆ3 Family Block Transfer Timing
A typical PLC-3 application might have the following configuration:
3 active I/O channels on one scanner
4 block transfer device on each channel
4 I/O chassis on each active channel
10 dynamic objects on PanelView screen
In this case, the typical time required for block transfer data to be
transferred to or from a PanelView Terminal (including terminal’s display
or input processing time) would be approximately 883 ms.
Calculating PLC-3 Block Transfer Timing
To calculate the typical time required to transfer “block transfer data” to or
from a PanelView Terminal (including terminal’s input or display
processing time), the following formula can be used:
Time (read or write) = PS + 2[CT] + TP
PS = Program Scan Time
CT = Channel Time
TP = PanelView Terminal Process Time
The following pages explain how to determine the above parameters.
Program Scan Time
The PLC-3 program scan time is typically 2.5 ms per 1K, when using a
mix of examine on/off and block instructions (1 ms/K for examine on/off
instructions only).
Channel Time
The time required for the scanner to complete a read or write depends on
the number of other block transfer devices on the same channel that are
enabled simultaneously. Channel Time (CT) is the time required for the
scanner to complete all block transfers on a particular channel. This will be
the time intervals between block transfers. Use the following formula to
determine CT—“channel time”:
CT = [Nominal Time x Number of BT on Channel] + [Number of Chassis
in Rack List – 1] x 9 ms