Snapshot Object

Overview

The Snapshot object gives a way of storing and recalling a set of logic values (a snapshot) whilst online. A Snapshot object can store a number of these snapshots, each of which can be stored and recalled at any time. Only one of the following inputs should be high at any one time: Store; Recall; Clear; Bypass. If more than one of these inputs is high at any one time, the object will be in an error condition during which time none of them will have any effect.

Store

To store a snapshot, the data is placed on the data inputs, the snapshot number is placed on the snapshot select inputs and the Store input is taken high.

Recall

Similarly, to recall a snapshot, the snapshot number is placed on the snapshot select inputs, and the Recall input is taken high. The object then places the stored data on the data output. As long as recall is kept high, any snapshots selected will immediately appear on the output.

Snapshot Selection

The snapshot select inputs can be interpreted as priority or binary.

Priority Mode: the lowest active input specifies the number
Binary Mode:   all the inputs specify a binary number

So for example, if only priority inputs S3 and S5 were active (0001 0100), snapshot 3 would be selected.

In binary, the same input 0001 0100, (B2 and B4 active) would be interpreted as binary, that is value 20, and because the first snapshot is stored at binary 0, is snapshot 21.

If set as binary, a pattern of 1010 for instance would store it as snapshot 6.

Clear

Clear will set the stored snapshot value for the selected location to zero. The data outputs will remain unchanged.

Bypass

To bypass the Snapshot object and pass data straight through from the data input to the data output, the Snapshot object can be put into bypass mode by setting the Bypass input high. This mode overrides the data that would be output by recall, although these actions still work internally.

Properties

Logic Inputs

Sets the number of logic inputs for the Snapshot function, selectable from 1 to 27. The number of logic outputs will automatically be set to the same.

Snapshot Selection Inputs

Sets the number of inputs to be used for selecting a Snapshot to be recalled or stored. Depending on whether the inputs are configured as priority or binary will affect how many inputs are available.

Maximum selection inputs
Priority: (28 - Number of Logic Inputs)
Binary  : 8

Snapshot Addressing

Sets the Snapshot selection to be Priority or Binary.

When set to Priority, only the lowest active snapshot selection line selects the snapshot. The lowest input, S1 has the highest priority. Each input selects a single snapshot so 3 lines allows the storage of 3 snapshots.

When set to Binary, the snapshot selection lines are interpreted as a binary number, so 3 lines allows the storage of 8 snapshots.

Clear Outputs

When set to YES the outputs will be cleared when the stored snapshot for the selected location is cleared.

Snapshot n

This is a list of the contents of each snapshot, which can be edited offline.