Telemark 880 - Section 5.6; Output Functions; Section 5.7; Softnodes and Sync Events

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SECTION 5.XX
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Output Functions
There are several ways to evaluate the result of a rung in the Model 880. A rung must have 1 and
only 1 output function. Some Output Functions are for use with edges and others are for use with steady
states.
There are several ways of describing edges in the I/O program of the Model 880. The Trip
function is used exclusively to force events in the Model 880. Arm and Drop are the other two output
functions that operate when triggered by edges, and operate on I/O outputs, softnodes and counters.
Output
The Output function (O) is used as a steady state output. It will take the evaluated state of the
rung and use the value as an output. It is common to use the output function for relays and softnodes. Not
available for events, counters, hardware inputs.
Trip
The Trip Function (T) can be used for providing a pulse to an output, either of a relay or softnode.
It is triggered by a positive Edge transition (something that goes from false to true). The output will stay
true for about 1 second, then go back to the false state. This is sometimes known as a 1-shot function. In
addition, all of the events of the Model 880 can only be triggered using this function. This is indicated in
Table 5.4, by having a 'T' in the valid function column.
Arm And Drop
There are two other functions that operate by triggering on edge transitions. These are called arm
and drop
(A and D). The identified output will become true when there is a positive edge on the arm
input. The output will remain true until something else makes it false. The drop function is the opposite of
arm. The output will become false on the positive edge of the drop input. These are different from the trip
function because the arm causes the output to go high and stay there. It takes a drop function to cause the
output to go back low. The arm and drop functions are to be used together. If you use arm on an output,
somewhere in the I/O program you must use a drop or clear on that output, unless the relay or output
activates and latches.
Set And Clear
There are 2 functions that may look like edge events, but they are level triggers. They are called
set and clear (S and C). A true condition on the set of an output will cause the output to become true and
stay that way even when the input condition later becomes false. This is known as a latching function.
The clear input will cause the output to become false when the clear becomes true. The clear function is
the opposite of the set function. (The set/clear and the arm/drop can be mixed and matched, i.e. set/drop or
arm/clear)
Note Remember that only a trip function can cause a trigger to an internal
event of the Model 880. If you try to program any other output to events, you will get an
error message.
Soft Nodes and Sync Events
Soft nodes in the Model 880 are a special type of I/O variable. Their ID numbers are 300 through
399. They can act as temporary storage areas for intermediate results. If you develop complex I/O rungs,
you can use these soft nodes to break these up into several simpler rungs. Devices such as counters and
shift registers can be implemented using soft nodes.
SECTION 5.6
Note
SECTION 5.7