Allen-Bradley MicroLogix 1400 User Manual

Publication 1766-RM001A-EN-P - October 2008
Programming Instructions Overview 97
Example - Using Indirect Addressing to Duplicate Indexed
Addressing
In this section, an indexed addressing example is shown first. Then an
equivalent indirect addressing example is shown. Indexed addressing is
supported by SLC 500 and MicroLogix 1000 programmable controllers.
The MicroLogix 1100, 1200, 1400, and 1500 do not support indexed
addressing. This example is shown for comparison purposes.
Indexed Addressing Example
The following ADD instruction uses an indexed address in the Source A
and Destination addresses. If the indexed offset value is 20 (stored in
S:24), the controller uses the data stored at the base address plus the
indexed offset to perform the operation.
In this example, the controller uses the following addresses:
Table 4.1
Operand Base Address Offset Value in S:24 Working Address
Source A N7:0 20 N7:20
Destination N15:0 20 N15:20
ADD
Add
Source A #N7:0
Source B 25
Dest #N15:0
ADD ADD
Add
Source A N7:20
Source B 25
Dest N15:20
ADD
Indexed Working
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Allen-Bradley MicroLogix 1400 Specifications

General

Processor	32-bit
Expansion Modules	Up to 7 expansion I/O modules
Power Supply	24V DC or 120/240V AC
Programming Software	RSLogix 500
Communication Ports	Ethernet, RS-232/RS-485 combo port
Controller Type	Programmable Logic Controller (PLC)
Series	MicroLogix
Digital Outputs	12
Analog Inputs	6 (embedded)
Analog Outputs	2 (embedded)
High-Speed Counter	6 high-speed counters
Pulse Output	2 (embedded)
Ethernet Port	Yes