9ć13, Program constants direct and indirect elements – Rockwell Automation 1785-LTx,D17856.2.1 Classic PLC-5 Programmable Controllers Users Manual User Manual
Page 130

Calculating Program Timing
Chapter 9
9-13
Category Words of
Memory
1
Time (
µ
s)
Integer or
Floating Point
False
Time (
µ
s)
Floating point
True
Time (
µ
s)
Integer
True
Title
Code
Miscellaneous
END
end
negligible
negligible
1
TND
temporary end
negligible
15
AFI
always false
15
13
ONS
one shot
28
30
2Ć3
DTR
data transitional
41
41
4Ć7
BTD
bit distributor
77
14
6Ć11
PID
PID loop control
608
34
5Ć9
BTR
block transfer read See Block Transfer BTR, BTW chapter
BTW
block transfer write
MSG
message See Message MSG chapter
W = number of elements acted on per scan
N = 2 x (number of integer file addresses) + 8 x (number of floatingĆpoint file addresses) + 6 x (number of timer, counter, or control
N 2 x (number of integer file addresses) + 8 x (number of floating point file addresses) + 6 x (number of timer, counter, or control
file addresses) + ( number of conversions between integer and floating point formats)
1
Use the smaller number if all addresses are below word 4096; use the larger number if all addresses are above 4096.
Use program constants in compare, compute, and file instructions to
improve instruction execution times. Integer constants and floating-point
constants execute in less than 1
µ
s. Note that if you program using
constants you must edit the program to change the constants. If you
program using data table addresses, you can change the values by simply
changing the value in the data table.
Directly Addressed Elements
Additional execution time for directly addressed elements depends on:
data types
location in memory, referenced to the beginning of all data files (output
file, word 0)
whether data is stored at the source or destination address
whether the instruction converts data
Table 9.P lists times to add to instruction execution times.
Program Constants
Direct and Indirect Elements