Allen-Bradley micrologix 1500 Reference Manual

Publication 1762-RM001C-EN-P
B-6 MicroLogix 1500 Memory Usage and Instruction Execution Time
MicroLogix 1500
Scan Time Worksheet
Calculate the scan time for your control program using the worksheet
below.
Communications Multiplier Table
Input Scan (sum of below)
Overhead (if expansion I/O is used) = 53 µs
Expansion Input Words X 3 µs (or X 7.5 µs if Forcing is used) =
Number of modules with Input words X 10 µs =
Input Scan Sub-Total =
Program Scan
Add execution times of all instructions in your program when executed true =
Program Scan Sub-Total =
Output Scan (sum of below)
Overhead (if expansion I/O used)
= 29 µs
Expansion Output Words X 2 µs (or X 6.5 µs if Forcing is used) =
Output Scan Sub-Total =
Communications Overhead
(1)
Worst Case = 1100 µs
Typical Case = 400 µs
Use this number if the communications port is configured, but not communicating to
any other device
= 150 µs
Use this number if the communications port is in Shutdown mode = 0 µs
Pick one of the four numbers for Channel 0
Pick one of the four numbers for Channel 1
Communications Overhead Sub-Total=
System Overhead
Add this number if your system includes a 1764-RTC, 1764-MM1RTC, or MM2RTC. = 80 µs
Add this number if your system includes a 1764-DAT = 530 µs
Housekeeping Overhead = 240 µs 240
System Overhead Sub-Total =
Totals
Sum of all
Multiply by Communications Multiplier from Table X
Time Tick Multiplier (X1.02)
Total Estimated Scan Time =
(1) Communications Overhead is a function of the device connected to the controller. This will not occur every scan.
Protocol
Multiplier at Various Baud Rates
38.4K 19.2K 9.6K 4.8K 2.4K 1.2K 600 300
Inactive
(1)
DF1 Full Duplex 1.39 1.20 1.13 1.10 1.09 1.08 1.08 1.08 1.00
DF1 Half Duplex 1.18 1.12 1.09 1.08 1.07 1.07 1.06 1.06 1.01
DH-485 N/A 1.14 1.10 N/A N/A N/A N/A N/A 1.06 at 19.2K
1.09 at 9.6K
Modbus
(2)
1.21 1.12 1.09 1.08 1.08 1.08 1.08 1.08 1.00
ASCII
(2)
1.52 1.33 1.24 1.20 1.19 1.18 1.18 1.17 1.00
Shut Down 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00
(1) Inactive is defined as No Messaging and No Data Monitoring. For DH-485 protocol, inactive means that the controller is not conne cted to a network.
(2) Applies to MicroLogix 1500 Series B Processors only.

Allen-Bradley micrologix 1500 Specifications

General

Brand	Allen-Bradley
Model	micrologix 1500
Category	Controller
Language	English