Appendix D
Estimating Scan Time
D–6
Suppose you have a system consisting of the following components:
System Configuration
Description
Catalog Number
Quantity
Description
1747-L514
1746-IA8
1746-IB16
1746-OA16
1746-OB8
1746-NIO4V
1
2
1
3
1
1
4K Processor
8 point 120VAC Input Module
16 point 24VDC Sinking Input Module
16 point 120VAC Relay Output Module
16 point 24VDC Sourcing Output Module
4 Channel Analog Combination Module
Since you are using the 1747-L514 processor, worksheet B must be filled
out. This is shown on page
D–7
.
The ladder program below is used in this application. The execution times
for the instructions (true state) are from appendix C. The total execution
time, 465 microseconds, is entered in the worksheet on page D–7.
The worksheet indicates that the total estimated scan time is 3.85
milliseconds minimum and 8.9 milliseconds maximum.
END
]/[
B3
1
( )
O:1.0
0
(EN)
(DN)
TON
TIMER ON DELAY
Timer
T4:0
Time Base
0.01
Preset
6000
Accum
] [
B3
0
]/[
T4:0
DN
] [
B3
45
]/[
T4:0
DN
] [
B3
9
]/[
B3
1
] [
T4:0
DN
GRT
GREATER THAN
Source A
T4:0.ACC
Source B
5999
TOD
TO BCD
Source
T4:0.ACC
Dest
S:13
MOV
MOVE
Source
S:13
Dest
O:1.0
Execution Times:
139 microseconds
38 microseconds
288 microseconds
Total: 465 microseconds
Example Scan Time
Calculation
