Allen-Bradley MicroLogix 1200 Reference Manual page 131

Use the OSR and OSF instructions to trigger an event to occur one time.
These instructions trigger an event based on a change of rung state, as
follows:
• Use the OSR instruction when an event must start based on the
false-to-true (rising edge) change of state of the rung.
• Use the OSF instruction when an event must start based on the
true-to-false (falling edge) change of state of the rung.
These instructions use two parameters, Storage Bit and Output Bit.
• Storage Bit - This is the bit address that remembers the rung state from
the previous scan.
• Output Bit - This is the bit address which is set based on a
false-to-true (OSR) or true-to-false (OSF) rung transition. The Output
Bit is set for one program scan.
To re-activate the OSR, the rung must become false. To re-activate the
OSF, the rung must become true.
Table 7.12 OSR Storage and Output Bit Operation
Rung State Transition
false-to-true (one scan)
true-to-true
true-to-false and false-to-false
Table 7.13 OSF Storage and Output Bits Operation
Rung State Transition
true-to-false (one scan)
false-to-false
false-to-true and true-to-true
Addressing Modes and File Types can be used as shown in the following
table:
Table 7.14 OSR and OSF Instructions Valid Addressing Modes and File Types
For definitions of the terms used in this table see Using the Instruction Descriptions on page4-2.
Data Files
Parameter
Storage Bit •
Output Bit • • • • •
Storage Bit
bit is set
bit is set
bit is reset
Storage Bit
bit is reset
bit is reset
bit is set
Function Files
•
•
Relay-Type (Bit) Instructions 7-7
Output Bit
bit is set
bit is reset
bit is reset
Output Bit
bit is set
bit is reset
bit is reset
Address Address
Mode Level
• •
• •
Publication 1762-RM001C-EN-P