Allen-Bradley MicroLogix 1400 User Manual

Publication 1766-RM001A-EN-P - October 2008
172 Relay-Type (Bit) Instructions
The ONS instruction is a retentive input instruction that triggers an event
to occur one time. After the false-to-true rung transition, the ONS
instruction remains true for one program scan. The output then turns OFF
and remains OFF until the logic preceding the ONS instruction is false
(this re-activates the ONS instruction).
The ONS Storage Bit is the bit address that remembers the rung state from
the previous scan. This bit is used to remember the false-to-true rung
transition.
Addressing Modes and File Types can be used as shown in the following
table:
TIP
The ONS instruction for the MicroLogix 1400 provides the same
functionality as the OSR instruction for the MicroLogix 1000 and SLC 500
controllers.
ONS Instruction Operation
Rung Transition Storage Bit Rung State after Execution
false-to-true (one scan) storage bit is set true
true-to-true storage bit remains set false
true-to-false,
false-to-false
storage bit is cleared false
ONS Instruction Valid Addressing Modes and File Types
For definitions of the terms used in this table see Using the Instruction Descriptions on page 92.
Parameter
Data Files Function Files
CS - Comms IOS - I/O DLS - Data Log
Address
Mode
Address Level
O I S B T, C, R N F ST L MG, PD RI/RIX PLS RTC HSC PTOX, PWMX STI EII BHI MMI LCD Immediate Direct Indirect Bit Word Long Word Element
Storage Bit • • • •
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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