Memory Copy

Copy to and from memory section

  • Library:
  • Simulink Support Package for Arduino Hardware/Utilities

    Embedded Coder Support Package for STMicroelectronics Discovery Boards/Utilities

    Simulink Coder Support Package for STMicroelectronics Nucleo Boards/Utilities

Description

In generated code, the Memory Copy block copies variables or data to and from processor memory as you have configured with block parameters. Your model can contain as many of these blocks as you require to manipulate memory on your processor.

Each block works with one variable, address, or set of addresses provided to the block. Using the parameters of this block you specify the source and the destination for the memory copy and options for initializing the memory locations.

At run time, you can change options like the memory stride and offset. You can write to memory at program initialization, at program termination, and at every sample time by selecting various parameters in the block. The initialization process occurs once, rather than occurring for every read and write operation.

With the custom source code options, the block enables you to add custom ANSI® C source code before and after each memory read and write (copy) operation.

Block Operations

This block performs operations at three periods during program execution: initialization, real-time operations, and termination. With the options for setting the memory initialization and termination, you control when and how the block initializes memory, copies to and from memory, and terminates memory operations. The parameters enable you to turn on and off memory operations in the three periods, independently of each other.

Copy Memory

When you use this block to copy an individual data element from the source to the destination, the block copies the element from the source in the source data type, and then casts the data element to the destination data type that you specify in the block parameters.

Ports

Input

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When reading the data from this input port, set the Copy from parameter to Input port. When you choose this option, an input port becomes available. The port label on the block changes to src, indicating that the block expects data to come from the input port.

To inherit data type from the incoming signal, set the source Data Type parameter to Inherit from input port. Specify the source Offset parameter as 0 and the source Stride parameter as 1. If you specify any other value for these parameters, you receive an error message that the specified values are invalid.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | Boolean

When reading the source address from this input port, set the Copy from parameter to Specified address and set the source Specify address source parameter to Input port. When you choose these options, an input port becomes available. The port label on the block changes to &src, indicating that the block expects the address to come from the input port. The ability to change the address dynamically means that you can the block to copy different variables by providing the variable address from an upstream block in your model.

When reading the address from the input port, change the source Data type from the default Inherit from input port to one of the data types in the Data type list. If you do not change the parameter value, you receive an error message. The error message indicates that the data type cannot be inherited because the input port does not exist.

Data Types: uint32

When reading the offset value of data from this input port, set the source Specify offset source parameter to Input port. The source Specify offset source parameter appears only when you select the Use offset when reading parameter.

When you choose this option, an input port becomes available. The port label on the block changes to src ofs, indicating that the block expects the offset value to come from the input port. This port enables your program to change the offset dynamically during execution by providing the offset value as an input to the block.

When reading the offset value from the input port, do not set the Copy from parameter to Input port. If you choose this option, you receive an error message that you cannot specify the source offset parameter as an input port when copying data from the input port.

Data Types: uint32

When reading the start address of the destination memory location from this input port, set the Copy to parameter to Specified address and set the destination Specify address source parameter to Input port. When you choose this option, an input port becomes available. The port label on the block changes to &dst, indicating that the block expects the address to come from the input port. The ability to change the address dynamically means that you can the block to copy different variables by providing the variable address from an upstream block in your model.

Data Types: uint32

When reading the offset value of the destination memory location from this input port, set the destination Specify offset source parameter to Input port. The destination Specify offset source parameter appears only when you select the Use offset when reading parameter.

When you choose this option, an input port becomes available. The port label on the block changes to dst ofs, indicating that the block expects the offset value to come from the input port. This port enables your program to change the offset dynamically during execution by providing the offset value as an input to the block.

When reading the offset from the input port, do not set the Copy to parameter to Output port. If you choose this option, you receive an error message that cannot specify the destination offset parameter as an input port when copying data to output port.

Data Types: uint32

Output

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When writing data to this output port, set the Copy to parameter to Output port. When you choose this option, an output port becomes available. The port label on the block changes to dst, indicating that the block writes data to the output port.

To inherit data type from the incoming signal, set the Data Type parameter to Inherit from source. Specify the destination Offset parameter as 0 and the destination Stride parameter as 1. If you specify any other value for these parameters, you receive an error message that the specified values are invalid.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | Boolean

Parameters

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The Memory Copy dialog box contains multiple tabs:

  • Source — Identifies the sequential memory location to copy from. Specify the data type, size, and other attributes of the source variable.

  • Destination — Specify the memory location to copy the source to and specify the attributes of the destination.

  • Options — Select various parameters to control the copy process.

Source

  • Input port — An input port becomes available. The port label on the block changes to src, indicating that the block expects data to come from the input port.

  • Specified address — The block reads the source address from the option that you select from the Specify address source parameter.

    If you set the Specify address source parameter to Specify via dialog, the block reads the source address that you specify in the Address parameter.

    If you set the Specify address source parameter to Input Port, an input port becomes available. The port label on the block changes to &src, indicating that the block expects the address to come from the input port

  • Specified source code symbol — The block reads data from the symbol (variable) that you specify in the Source code symbol parameter.

If you select Specified address or Specified source code symbol for the Copy from parameter, change Data type from the default Inherit from input port to one of the data types on the Data type list.

  • Specify via dialog — The block reads data from the memory location that you specify in the Address parameter.

  • Input port — An input port becomes available. The port label on the block changes to &src, indicating that the block expects the source address to come from the input port. The ability to change the address dynamically means that you can the block to copy different variables by providing the variable address from an upstream block in your model.

Dependencies

This parameter appears only when you set the Copy from parameter to Specified address.

The block does not verify whether the symbol is valid. A symbol is valid only if it has an entry in the symbol table. If it is not valid you get an error when you try to compile, link, and run your generated code.

If the symbol contains a scalar value, specify & before the symbol in this parameter. If the symbol contains a vector value, specify only the symbol in this parameter.

Dependencies

This parameter appears only when you set the Copy from parameter to Specified source code symbol.

Specify the address in a decimal format or as a hexadecimal string with single quotation marks. When you specify the address as a hexadecimal string, pass that string as a parameter to the hex2dec function. This function converts the string from the hexadecimal format to the decimal format. The following example converts 0x1000 to its decimal form.

4096 = hex2dec('1000');

For this example, you can specify either 4096 or hex2dec('1000') as the address.

Dependencies

This parameter appears only when you set the Copy from parameter to Specified address and set the Specify address source to Specify via dialog.

Use this parameter to specify the data type of your input data. When you set this parameter to Inherit from input port, the block inherits the data type from the value at the block input port.

Note

If you select the Copy from parameter to Specified address or Specified source code symbol, change the Data type parameter from the default Inherit from input port to one of the data types on the Data type list.

When you select this parameter, the block reads the source offset from the option that you select from the Specify offset source parameter. When you clear this parameter, the block reads data from the start address that you specify in the Copy from parameter.

  • Specify via dialog — The block reads the offset value that you specify in the Offset parameter.

  • Input port — An input port becomes available. The port label on the block changes to src ofs, indicating that the block expects the offset value to come from the input port. This port enables your program to change the offset dynamically during execution by providing the offset value as an input to the block.

Dependencies

This parameter appears only when you select the Use offset when reading parameter.

An Offset instructs the block whether to copy the first element of data at the input address, or skip values before starting to copy the input to the destination. The Offset defines how many input elements to skip before copying the first value to the destination.

Dependencies

This parameter appears only when you select the Use offset when reading parameter.

Specify spacing between the elements when reading the input data. A stride value equal to 1 means that the generated code reads the input data sequentially. When you add a stride value that is more than 1, the block skips that number of elements and reads the elements from the resulting address.

The next two figures illustrate the stride concept. In the first figure, you see data copied without a stride.

The second figure shows a stride value equal to 2. A stride value 2 is applied when the block is copying the input to an output location. You can specify a stride value for the output from the Destination tab by using the Stride parameter.

Destination

  • Output port — An output port becomes available. The port label on the block changes to dst, indicating that the block writes data to the output port.

  • Specified address — The block copies data to the memory location that you that you specify in the Specify address source parameter.

    If you set the Specify address source parameter to Specify via dialog, the block reads the destination address that you specify in the Address parameter.

    If you set the Specify address source parameter to Input Port, an input port becomes available. The port label on the block changes to &dst, indicating that the block expects the destination address to come from the input port

  • Specified source code symbol — The block copies data to the symbol (variable) that you specify in the Source code symbol parameter.

  • Specify via dialog — The block writes data to the location that you specify in the Address parameter.

  • Input port — An input port becomes available. The port label on the block changes to &dst, indicating that the block expects the destination address to come from the input port. The ability to change the address dynamically means that you can the block to copy different variables by providing the variable address from an upstream block in your model.

Dependencies

This parameter appears only when you set the Copy to parameter to Specified address.

The block does not verify whether the symbol is valid. A symbol is valid only if it has an entry in the symbol table. If it is not valid you get an error when you try to compile, link, and run your generated code.

If the symbol contains a scalar value, specify & before the symbol in this parameter. If the symbol contains a vector value, specify only the symbol in this parameter.

Dependencies

This parameter appears only when you set the Copy to parameter to Specified source code symbol.

Specify the address in a decimal format or as a hexadecimal string with single quotation marks. When you specify the address as a hexadecimal string, pass that vector as a parameter to the hex2dec function. This function converts the string from hexadecimal format to decimal format. The following example converts Ox2000 to decimal form.

8192 = hex2dec('2000');

For this example, you can specify either 8192 or hex2dec('2000') as the address.

Dependencies

This parameter appears only when you set the Copy to parameter to Specified address and set the Specify address source to Specify via dialog.

Use this parameter to specify the data type of your output. When you set this parameter to Inherit from source, the block inherits the data type from the input signal at the block input port.

When you select this parameter, the block reads the offset from the option that you select from the Specify offset source parameter. When you clear this parameter, the block reads data from the start address from the option that you specify in the Copy to parameter.

  • Specify via dialog — The block reads the offset value that you specify in the Offset parameter.

  • Input port — An input port becomes available. The port label on the block changes to dst ofs, indicating that the block expects the offset value to come from the input port. This port enables your program to change the offset dynamically during execution by providing the offset value as an input to the block.

Dependencies

This parameter appears only when you select the Use offset when writing parameter.

An Offset instructs the block whether to write the first element of data to the start address of destination, or skip one or more locations at the destination before writing the output. The Offset defines how many values to skip in the destination before writing the first value to the destination.

Dependencies

This parameter appears only when you select the Use offset when writing parameter.

Specify the spacing between the elements when writing the output data. A stride value equal to one means that the generated code writes the input data sequentially to the destination in consecutive locations. When you add a stride value that is more than 1, the output data is stored not sequentially, but skips elements equal to the stride.

This figure shows a stride value of 3 applied to writing the input to an output location. You can specify a stride value for the input from the Source tab by using the Stride parameter. As shown in the figure, you can apply input and output stride at the same time to manipulate your memory more fully.

The default value Inf instructs the block to use a constant sample time. When you specify the Sample time as -1, the Memory Copy block inherits the sample time from the input. When there are no block inputs, the block inherits the sample time from the Simulink® model.

Options

When you select this option, you direct the block to initialize the memory location to a specific value when you initialize your program at run time. After you select this option, use the Specify initialization value source parameter to set the value that you want. Alternately, you can direct the block to get the initial value from the block input.

If you select this parameter, set the destination Copy to parameter to either Specified address or Specified source code symbol. If you do not change the parameter value, you receive an error message that memory cannot be set at initialization when the destination is output port.

  • Specify constant value — Set a single value to use when your program initializes memory.

    The block reads the initialization value from the value that you specify in the Initialization value (constant) parameter.

  • Specify source code symbol — Specifies a variable (a symbol) to use for the initial value.

    The block reads the initialization value from the symbol that you specify in the Initialization value (source code symbol) parameter. The block does not verify whether the symbol is valid. A symbol is valid only if it has an entry in the symbol table. If it is not valid, you get an error when you try to compile, link, and run your generated code.

Dependencies

This parameter appears only when you select the Set memory value at initialization parameter.

Dependencies

This parameter appears only when you select the Set memory value at initialization parameter and set the Specify initialization value source to Specify constant value.

When you specify a symbol, the block does not verify whether the symbol is valid. A symbol is valid only if it has an entry in the symbol table. If it is not valid, you get an error when you try to compile, link, and run your generated code.

Dependencies

This parameter appears only when you select the Set memory value at initialization parameter and set the Specify initialization value source to Specify source code symbol.

The initialization value is treated as a string of bits for the mask.

The block performs the bitwise operation on the initialization value to manipulate register contents at the bit level. The operator that you specify in the Bitwise operator parameter determines the bitwise operation.

Note

To use your initialization value as a mask, set the destination Copy to parameter to either Specified address or Specified source code symbol.

Dependencies

This parameter appears only when you select the Set memory value at initialization parameter.

To use the initialization value as a mask, from the Bitwise operator list, select one of the entries listed in this table.

Bitwise Operator List Entry

Description

bitwise AND

Apply the mask value as a bitwise AND to the value in the register.

bitwise OR

Apply the mask value as a bitwise OR to the value in the register.

bitwise exclusive OR

Apply the mask value as a bitwise exclusive OR to the value in the register.

left shift

Shift the bits in the register to the left by the number of bits represented by the initialization value. For example, if your initialization value is 3, the block shifts the register value to the left by 3 bits. In this case, the value must be a positive integer.

right shift

Shift the bits in the register to the right by the number of bits represented by the initialization value. For example, if your initialization value is 6, the block shifts the register value to the right by 6 bits. In this case, the value must be a positive integer.

Dependencies

This parameter appears only when you select the Apply initialization value as mask parameter.

This parameter initializes memory when the program starts to access the target memory location and directs the program to set memory to a specific value when the program terminates.

This parameter appears only when you select the Set memory value at termination parameter.

This Memory Copy block performs operations at three periods during program execution: initialization, real-time operations, and termination. When you select this parameter, the block performs only the memory initialization and termination operations. It does not copy data during real-time operations.

The block inserts a custom ANSI C code that you specify in the Custom code parameter before the write operation.

You can use the custom code capability to lock and unlock registers before and after accessing them. For example, some processors have registers that you want to unlock with the EALLOW macro before your program accesses them.

The code that you specify in this parameter is the code that appears in the generated code.

Dependencies

To enable this parameter, select the Insert custom code before memory write parameter.

The block inserts a custom ANSI C code that you specify in the Custom code parameter after the write operation.

You can use the custom code capability to lock and unlock registers before and after accessing them. For example, some processors have registers that you want to lock with the EDIS macro after your program accesses them.

The code that you specify in this parameter is the code that appears in the generated code.

Dependencies

This parameter appears only when you select the Insert custom code after memory write parameter.

More About

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Introduced in R2016b