Bit Instructions

The XIC and XIO instructions are input instructions.

Input instructions do not alter data. The instructions simply check the data referenced by the associated tag and executes logic based on the data.

In the case of the XIC instruction

when the tags value is 1 the instruction is true enabling instructions to the right to execute. If the tags value is 0 the instruction is false disabling instructions to the right.

In the case of the XIO instruction

when the tags value is 0 the instruction is true enabling instructions to the right to execute. If the tags value is 1 the instruction is false disabling instructions to the right.

To summarize, the XIC and XIO bit instructions look at the data addressed by the associated tag and allow instructions to the right to execute or not. These instructions do not manipulate data addressed by tags. As a result there is no limit to the amount or combination of these instructions that can be used in a program that reference a single tag.    

The OTE bit instruction is energized when all conditional logic to the left of the instruction is true. The OTE instruction manipulates the data pointed to by the associated tag. When energized the OTE instruction will write a value of 1 to the associated tags address.  When not energized the OTE instruction will write a value of 0 to the associated tags address.

The important thing to note about the OTE instruction is that the written value, either 1 or 0 is good for one program scan. For example suppose an OTE instruction set a value of 1.  That value will retain the 1 through an entire program scan. Once the scan has wrapped back around to the OTE instruction and the preceding logic is true the 1 value will be retained for another scan, however if the preceding logic is false a 0 will be written to the associated tags data address.

To summarize an OTE instruction writes either a 1 or a 0 to a tags data address. A tag is an address that points to a memory location that holds data, in this case either a 1 or a 0.

Important: You can associate one OTE instruction per unique tag. There is nothing in RSLogix 5000 software that will stop you from using more than one OTE instruction per tag, however as a good rule of thumb don’t do it, ever.

For example, if you have a Boolean tag named MY_BOOL it should be used once for output instruction such as an OTE. The tag can be referenced any number of times for input instructions like XIC.

The OTL and OTU instructions

work together to set data to a 1 or 0. The OTL instruction sets the data addressed by the associated tag to a 1 while the OTU instruction sets the data to a 0.

Unlike the OTE instruction the bit set by an OTL instruction is set to a 1 and will remain unchanged regardless of the preceding conditional logic until an OTU instruction referencing the same tag is set. The data will then be changed to a 0. Unlike the OTE the OTL and OTU instructions can reference the same tag  more than once in a program.

The ONS or OneShsot

is an output instruction that manipulates data addressed by the associated tag. When the logic left of the ONS instruction is true a 1 will be written to the associated tags address and the logic after the ONS instruction will execute for one program scan. When the instruction is scanned again and the preceding logic is true it will read the 1 referenced by the tag. The instruction will then set the logic to the right of the instruction false. When the logic to the left of the ONS instruction is false the instruction will write a 0 to the addressed data resetting the data for another oneshot.