Data Store Write

Write data to data store

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Libraries:
Simulink / Signal Routing

Description

The Data Store Write block copies the value at its input to the named data store. Each write operation performed by a Data Store Write block writes over the data store or a selected portion thereof and replaces the previous contents.

The data store to which this block writes is determined by the location of the Data Store Memory block or signal object that defines the data store. For more information, see Data Stores and Data Store Memory. The size of the data store is set by the signal object or the Data Store Memory block that defines and initializes the data store. Each Data Store Write block that writes to that data store can write up to the amount of data in the data store.

More than one Data Store Write block can write to the same data store. However, if two Data Store Write blocks attempt to write to the same data store during the same simulation step, results are unpredictable.

Obtaining correct results from data stores requires ensuring that data store reads and writes occur in the expected order. For details, see Order Data Store Access and Data Store Diagnostics.

You can log the values of a local or global data store data variable for all the steps in a simulation. For details, see Log Data Stores.

You can select a Data Store Read, Data Store Write, or Data Store Memory block to highlight blocks related to it. To show a related block in an open diagram or new tab, pause on the ellipsis that appears after selection. Then, select Related Blocks from the action bar. When multiple blocks correspond to the selected block, a list of related blocks opens. You can filter the list of related blocks by entering a search term in the text box. After you select a related block from the list, window focus goes to the open diagram or new tab that shows the related block.

Examples

Share Data Store Between Instances of a Reusable Algorithm

To reuse an algorithm, instead of copying and pasting the blocks, you can encapsulate them in a separate model file. Then, you can refer to the model repeatedly with Model blocks. Each Model block is a standalone instance of the algorithm.

Open Model

Ports

Input

Port_1 — Values to write to data store

scalar | vector | matrix | N-D array

Values to write to the specified data store. The Data Store Write block accepts a real or complex signal.

You can use an array of buses with a Data Store Write block. For details about defining and using an array of buses, see Group Nonvirtual Buses in Arrays of Buses.

To assign a subset of the bus or matrix elements to the associated data store, use the Element Assignment pane. The Data Store Write block icon reflects the elements that you specify. For details, see Accessing Specific Bus and Matrix Elements.

Data Types: single | double | half | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | fixed point | enumerated | bus | image

IdxN — Nth index signal

scalar | vector

External port specifying an index for the assignment of the corresponding data store subelements.

Dependencies

To enable an external index port, on the Element Assignment tab, select Enable indexing. Then, in the Nth row of the Index Option table, set Index Option to Index vector (port) or Starting index (port).

Data Types: int8 | int16 | int32 | uint8 | uint16

Parameters

Parameters

Data store name — Name of data store to which block writes

A (default) | name of data store

Specify the name of the data store to which this block writes data. The adjacent list provides the names of Data Store Memory blocks that exist at the same level in the model as the Data Store Write block or at higher levels. The list also includes all Simulink.Signal objects in the base and model workspaces. To change the name, select a name from the list or enter the name directly in the edit field.

When compiling a model containing this block, Simulink^® searches the model upwards from the level of the block for a Data Store Memory block having the specified data store name. If Simulink does not find such a block, it searches the model workspace and the MATLAB^® workspace for a Simulink.Signal object having the same name. If Simulink finds a signal object, it creates a hidden Data Store Memory block at the root level of the model with the properties specified by the signal object and an initial value set to an array of zeros. The dimensions of that array are inherited from the Dimensions property of the signal object.

If Simulink finds neither the Data Store Memory block nor the signal object, it halts the compilation and displays an error. See Symbol Resolution for more information about the search path.

Programmatic Use

Block Parameter: DataStoreName

Type: character vector

Values: data store name

Default: 'A'

Data store memory block — Data Store Memory block name

block path

This parameter is read-only.

This field lists the Data Store Memory block that initialized the store to which this block writes.

Corresponding Data Store Read blocks — List of corresponding Data Store Read blocks

block path

This parameter is read-only.

This field lists the path to all Data Store Read blocks with the same data store name as this block that are in the same (sub)system or in any subsystem below it in the model hierarchy. Click any entry in this list to highlight the corresponding block in your model.

Sample time — Sample time

-1 (default) | scalar | vector

The sample time, which controls when the block writes to the data store. A value of -1 indicates that the sample time is inherited. See Specify Sample Time for more information.

Programmatic Use

Block Parameter: SampleTime

Type: character vector

Values: scalar | vector

Default: '-1'

Element Assignment

Elements in the array (Signals in the bus) — Elements in associated data store

character vector (no default)

List of elements in the associated data store. For data stores with arrays, you can write the whole data store, or you can assign one or more elements to the whole data store. For data stores with a bus data type, you can expand the tree to view and select the bus elements. The list displays the maximum dimensions for each element in parentheses.

If Enable indexing is not selected, select an element and use one of the following approaches:

• Click Select>> to display that element and all its subelements in the Selected element(s) list.

• Use the Specify element(s) to assign edit box to specify the subelements that you want to select for writing. Then click Select>>.

To select multiple elements, repeat the above procedure for each element.

Alternatively, you can select Enable indexing, then select a single element and specify the subelements dynamically using the Index Option parameter.

To refresh the display and reflect modifications to the array or bus used in the data store, click Refresh.

Dependencies

The prompt for this section (Elements in the array or Signals in the bus) depends on the type of data in the data store.

Programmatic Use

Block Parameter: DataStoreElements

Type: character vector

Values: pound-delimited list of elements (See Specification using the command line.)

Default: ''

Specify element(s) to assign — MATLAB expression defining the elements to assign

character vector (no default)

Enter a MATLAB expression to define the specific element that you want to write, then click Select>> to add the element to the Assigned element(s) table. Repeat to select additional elements.

For example, for a data store named DSM that has maximum dimensions of [3,5], you could enter expressions such as DSM(2,4) or DSM([1 3],2) in the edit box. See Accessing Specific Bus and Matrix Elements.

To apply the element selection, click OK or Apply.

Dependencies

The Specify element(s) to assign edit box appears only if Enable indexing is not selected.

Programmatic Use

Block Parameter: DataStoreElements

Type: character vector

Values: pound-delimited list of elements (See Specification using the command line.)

Default: ''

Assigned element(s) — List of selected elements

character vector (no default)

Elements that you select for assignment. The Data Store Write block icon displays an input port for each element that you specify.

To change the order of bus or matrix elements in the list, select the element in the list and click Up or Down. Changing the order of the elements in the list changes the order of the ports. To remove an element, click Remove.

Dependencies

The Assigned element(s) table appears only if Enable indexing is not selected.

Programmatic Use

Block Parameter: DataStoreElements

Type: character vector

Values: pound-delimited list of elements (See Specification using the command line.)

Default: ''

Enable indexing — Enable indexing to specify subelements of data store element to write

'off' (default) | 'on'

Select this parameter to enable indexing similar to that used by the Assignment block, whereby you can dynamically specify indices of subelements to write by using one or more index input ports, as well as specifying indices by using the block dialog. A Data Store Write block can write to only a single element of a data store (that is, a single signal in a bus) when this parameter is selected. To write to multiple elements of a data store using dynamic indexing, use multiple Data Store Write blocks.

Clear this parameter to disable Assignment block-style indexing. You can select multiple data store elements to write, but you can specify which subelements to write only by using the block dialog.

Note

Do not select Enable indexing if the associated data store contains only a single, scalar element.

Programmatic Use

Block Parameter: EnableIndexing

Type: character vector

Values: 'off' | 'on'

Default: 'off'

Number of dimensions — Number of dimensions of data store element

1 (default) | positive integer

Number of dimensions of selected data store element. You must explicitly indicate this number.

Dependencies

This parameter is enabled only if Enable indexing is selected.

Programmatic Use

Block Parameter: NumberOfDimensions

Type: character vector

Values: positive integer

Default: '1'

Index mode — Index mode

One-based (default) | Zero-based

Select the indexing mode. If One-based is selected, an index of 1 specifies the first element of the input vector. If Zero-based is selected, an index of 0 specifies the first element of the input vector.

Dependencies

This parameter is enabled only if Enable indexing is selected.

Programmatic Use

Parameter: IndexMode

Type: character vector

Values: 'Zero-based' | 'One-based'

Default: 'One-based'

Index Option — Index method for subelements

Index vector (dialog) (default) | Select all | Index vector (port) | Starting index (dialog) | Starting index (port)

Define, by dimension, how the subelements of the selected data store element are to be indexed. From the list, select:

Menu Item	Action
Select all	Disables the Index column. All subelements are assigned.
Index vector (dialog)	Enables the Index column. Enter a vector containing the indices of subelements to be assigned values.
Index vector (port)	Disables the Index column. The relevant index port defines the indices of subelements to be assigned values.
Starting index (dialog)	Enables the Index column. Enter the starting index of the range of subelements to be assigned values. The size of the range is inherited from the size of relevant dimension of the input data signal.
Starting index (port)	Disables the Index column. The relevant index port defines the starting index of the range of elements to be assigned values. The size of the range is inherited from the size of relevant dimension of the input data signal.

The Index column is displayed as relevant.

Dependencies

This parameter is enabled only if Enable indexing is selected.

Programmatic Use

Parameter: IndexOptionArray

Type: character vector

Values: 'Select all' | 'Index vector (dialog)' | 'Index vector (port)' | 'Starting index (dialog)' | 'Starting index (port)'

Default: 'Index vector (dialog)'

Index — Indices or starting index of subelements

1 (default) | integer | vector of integers

If the Index Option is Index vector (dialog), enter a vector containing the indices of each subelement to write.

If the Index Option is Starting index (dialog), enter the starting index of the range of subelements to write.

Dependencies

This parameter is enabled only if Enable indexing is selected and the Index Option for the dimension is Index vector (dialog) or Starting index (dialog).

Programmatic Use

Parameter: IndexParamArray

Type: character vector

Values: cell array

Default: '{ }'

Block Characteristics

Data Types	Boolean | bus | double | enumerated | fixed point | half | integer | single | string
Direct Feedthrough	no
Multidimensional Signals	yes
Variable-Size Signals	no
Zero-Crossing Detection	no

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Fixed-Point Conversion
Design and simulate fixed-point systems using Fixed-Point Designer™.

Version History

Introduced before R2006a