PSoC™ 6 MCU: Protection units

This example demonstrates how to use the protection units to isolate the CM0+ CPU memory from CM4. This example uses FreeRTOS (v10.3.1).

See the "PSoC™ 6 MCU dual-CPU development" section in AN215656 – PSoC™ 6 MCU dual-CPU system design for instructions on how to develop dual-CPU applications.

View this README on GitHub.

Provide feedback on this code example.

Requirements

• ModusToolbox™ software v3.0 or later (tested with v3.0)
• Board support package (BSP) minimum required version: 4.0.0
• Programming language: C
• Associated parts: All PSoC™ 6 MCU parts

Supported toolchains (make variable 'TOOLCHAIN')

• GNU Arm® embedded compiler v10.3.1 (GCC_ARM) - Default value of TOOLCHAIN
• Arm® compiler v6.16 (ARM)
• IAR C/C++ compiler v9.30.1 (IAR)

Supported kits (make variable 'TARGET')

• PSoC™ 6 Wi-Fi Bluetooth® prototyping kit (CY8CPROTO-062-4343W) – Default value of TARGET
• PSoC™ 6 Wi-Fi Bluetooth® pioneer kit (CY8CKIT-062-WIFI-BT)
• PSoC™ 6 Bluetooth® LE pioneer kit (CY8CKIT-062-BLE)
• PSoC™ 6 Bluetooth® LE prototyping kit (CY8CPROTO-063-BLE)
• PSoC™ 62S2 Wi-Fi Bluetooth® pioneer kit (CY8CKIT-062S2-43012)
• PSoC™ 62S1 Wi-Fi Bluetooth® pioneer kit (CYW9P62S1-43438EVB-01)
• PSoC™ 62S1 Wi-Fi Bluetooth® pioneer kit (CYW9P62S1-43012EVB-01)
• PSoC™ 62S3 Wi-Fi Bluetooth® prototyping kit (CY8CPROTO-062S3-4343W)
• Rapid IoT connect developer kit (CYSBSYSKIT-DEV-01)
• PSoC™ 62S4 pioneer kit (CY8CKIT-062S4)
• PSoC™ 62S2 evaluation kit (CY8CEVAL-062S2, CY8CEVAL-062S2-LAI-4373M2, CY8CEVAL-062S2-MUR-43439M2)

Hardware setup

This example uses the board's default configuration. See the kit user guide to ensure that the board is configured correctly.

Note: The PSoC™ 6 Bluetooth® LE pioneer kit (CY8CKIT-062-BLE) and the PSoC™ 6 Wi-Fi Bluetooth® pioneer kit (CY8CKIT-062-WIFI-BT) ship with KitProg2 installed. The ModusToolbox™ software requires KitProg3. Before using this code example, make sure that the board is upgraded to KitProg3. The tool and instructions are available in the Firmware Loader GitHub repository. If you do not upgrade, you will see an error like "unable to find CMSIS-DAP device" or "KitProg firmware is out of date".

Software setup

Install a terminal emulator if you don't have one. Instructions in this document use Tera Term.

This example requires no additional software or tools.

Using the code example

Create the project and open it using one of the following:

In Eclipse IDE for ModusToolbox™ software

1. Click the New Application link in the Quick Panel (or, use File > New > ModusToolbox Application). This launches the Project Creator tool.

2. Pick a kit supported by the code example from the list shown in the Project Creator - Choose Board Support Package (BSP) dialog.

   When you select a supported kit, the example is reconfigured automatically to work with the kit. To work with a different supported kit later, use the Library Manager to choose the BSP for the supported kit. You can use the Library Manager to select or update the BSP and firmware libraries used in this application. To access the Library Manager, click the link from the Quick Panel.

   You can also just start the application creation process again and select a different kit.

   If you want to use the application for a kit not listed here, you may need to update the source files. If the kit does not have the required resources, the application may not work.

3. In the Project Creator - Select Application dialog, choose the example by enabling the checkbox.

4. (Optional) Change the suggested New Application Name.

5. The Application(s) Root Path defaults to the Eclipse workspace which is usually the desired location for the application. If you want to store the application in a different location, you can change the Application(s) Root Path value. Applications that share libraries should be in the same root path.

6. Click Create to complete the application creation process.

For more details, see the Eclipse IDE for ModusToolbox™ software user guide (locally available at {ModusToolbox™ software install directory}/ide_{version}/docs/mtb_ide_user_guide.pdf).

In command-line interface (CLI)

ModusToolbox™ software provides the Project Creator as both a GUI tool and the command line tool, "project-creator-cli". The CLI tool can be used to create applications from a CLI terminal or from within batch files or shell scripts. This tool is available in the {ModusToolbox™ software install directory}/tools_{version}/project-creator/ directory.

Use a CLI terminal to invoke the "project-creator-cli" tool. On Windows, use the command line "modus-shell" program provided in the ModusToolbox™ software installation instead of a standard Windows command-line application. This shell provides access to all ModusToolbox™ software tools. You can access it by typing modus-shell in the search box in the Windows menu. In Linux and macOS, you can use any terminal application.

This tool has the following arguments:

Argument	Description	Required/optional
--board-id	Defined in the <id> field of the BSP manifest	Required
--app-id	Defined in the <id> field of the CE manifest	Required
--target-dir	Specify the directory in which the application is to be created if you prefer not to use the default current working directory	Optional
--user-app-name	Specify the name of the application if you prefer to have a name other than the example's default name	Optional

The following example clones the "mtb-example-psoc6-dual-cpu-protection-units-freertos" application with the desired name "Psoc6DualCpuProtection" configured for the CY8CKIT-062-WIFI-BT BSP into the specified working directory, C:/mtb_projects:

project-creator-cli --board-id CY8CKIT-062-WIFI-BT --app-id mtb-example-psoc6-dual-cpu-protection-units-freertos --user-app-name Psoc6DualCpuProtection --target-dir "C:/mtb_projects"

Note: The project-creator-cli tool uses the git clone and make getlibs commands to fetch the repository and import the required libraries. For details, see the "Project creator tools" section of the ModusToolbox™ software user guide (locally available at {ModusToolbox™ software install directory}/docs_{version}/mtb_user_guide.pdf).

To work with a different supported kit later, use the Library Manager to choose the BSP for the supported kit. You can invoke the Library Manager GUI tool from the terminal using make library-manager command or use the Library Manager CLI tool "library-manager-cli" to change the BSP.

The "library-manager-cli" tool has the following arguments:

Argument	Description	Required/optional
--add-bsp-name	Name of the BSP that should be added to the application	Required
--set-active-bsp	Name of the BSP that should be as active BSP for the application	Required
--add-bsp-version	Specify the version of the BSP that should be added to the application if you do not wish to use the latest from manifest	Optional
--add-bsp-location	Specify the location of the BSP (local/shared) if you prefer to add the BSP in a shared path	Optional

Following example adds the CY8CPROTO-062-4343W BSP to the already created application and makes it the active BSP for the app:

library-manager-cli --project "C:/mtb_projects/MyHelloWorld" --add-bsp-name CY8CPROTO-062-4343W --add-bsp-version "latest-v4.X" --add-bsp-location "local"

library-manager-cli --project "C:/mtb_projects/MyHelloWorld" --set-active-bsp APP_CY8CPROTO-062-4343W

In third-party IDEs

Use one of the following options:

• Use the standalone Project Creator tool:

  1. Launch Project Creator from the Windows Start menu or from {ModusToolbox™ software install directory}/tools_{version}/project-creator/project-creator.exe.

  2. In the initial Choose Board Support Package screen, select the BSP, and click Next.

  3. In the Select Application screen, select the appropriate IDE from the Target IDE drop-down menu.

  4. Click Create and follow the instructions printed in the bottom pane to import or open the exported project in the respective IDE.

• Use command-line interface (CLI):

  1. Follow the instructions from the In command-line interface (CLI) section to create the application, and then import the libraries using the make getlibs command.

  2. Export the application to a supported IDE using the make <ide> command.

  3. Follow the instructions displayed in the terminal to create or import the application as an IDE project.

For a list of supported IDEs and more details, see the "Exporting to IDEs" section of the ModusToolbox™ software user guide (locally available at {ModusToolbox™ software install directory}/docs_{version}/mtb_user_guide.pdf).

Operation

1. Connect the board to your PC using the provided USB cable through the KitProg3 USB connector.

2. Open a terminal program and select the KitProg3 COM port. Set the serial port parameters to 8N1 and 115200 baud.

3. Program the board using one of the following:

   Using Eclipse IDE for ModusToolbox™ software

   1. Select the application project in the Project Explorer.

   2. In the Quick Panel, scroll down, and click <Application Name> Program (KitProg3_MiniProg4).

   Using CLI

   From the terminal, execute the make program command to build and program the application using the default toolchain to the default target. The default toolchain and target are specified in the application's Makefile but you can override those values manually:

   make program TOOLCHAIN=<toolchain>
   

   Example:

   make program TOOLCHAIN=GCC_ARM
   

4. After programming, the application starts automatically. Confirm that "<CE title>" is displayed on the UART terminal.

5. Type listmap to print the memory map.

   Figure 1. Memory map print

   

6. Use the commands read and/or write to access the Shared SRAM and CM4 App sections. Note that you can read and write to the SRAM and read from the user flash.

7. Use the commands read and/or write to access the CM0+ App sections. Note that a fault occurs.

Debugging

You can debug the example to step through the code. In the IDE, use the <Application Name> Debug (KitProg3_MiniProg4) configuration in the Quick Panel. For details, see the "Program and debug" section in the Eclipse IDE for ModusToolbox™ software user guide.

Note: (Only while debugging) On the CM4 CPU, some code in main() may execute before the debugger halts at the beginning of main(). This means that some code executes twice – once before the debugger stops execution, and again after the debugger resets the program counter to the beginning of main(). See KBA231071 to learn about this and for the workaround.

Design and implementation

In this code example, the flash and SRAM are divided into two main sections: CM0+ app and CM4 app. There is also a shared SRAM section so that data can be shared between the two CPUs.

Figure 2. Protection unit memory map (2 MB of flash device)

Each section is protected using the shared memory protection unit (SMPU) with a pre-defined protection context (PC). The following table shows the protection units configured in this example for a PSoC™ 6 MCU device with 2 MB of flash.

Section	Bus master	Memory	SMPU	Start address	Size	Access attributes	Secure	Protection context
CM0+ app	CM0+	Flash	13	0x1000_0000	256 KB	R/W/X	Yes	PC = 1
CM4 app	CM4	Flash	11	0x1004_0000	1792 KB	R/W/X	No	PC = 4
CM0+ SRAM	CM0+	SRAM	12	0x0800_0000	128 KB	R/W	Yes	PC = 1
Shared SRAM	CM0+ / CM4	SRAM	10	0x0801_0000	128 KB	R/W	No	PC = 1,4
CM4 SRAM	CM4	SRAM	9	0x0802_0000	768 KB	R/W	No	PC = 4

When using other PSoC™ 6 MCU devices, the following memory size applies to each section:

Section	Size
CM0+ app	FLASH_SIZE / 8
CM4 app	FLASH_SIZE - FLASH SIZE / 8
CM0+ SRAM	SRAM_SIZE / 8
Shared SRAM	SRAM_SIZE / 8
CM4 SRAM	SRAM_SIZE - SRAM_SIZE / 4

Note: If the device has 288 KB of SRAM, use SRAM_SIZE = 256 KB instead.

The CM0+ CPU is responsible to configure all the SMPU and PC. It also configures the bus master to be assigned to a PC. To learn how to configure the SMPU, see this blog post. Once all the protections units are configured, CM0+ transitions the following bus masters to their respective PC values:

Bus master	PC
CM0+	1
CM4	4
Test Controller	1

Once the CM0+ bus master's PC is set to '1', it locks all the protections in place.

The CM4 CPU implements a command console over the UART. The following commands are supported:

Command	Description
listmap	Print the memory map
read <address>	Attempt to read the given address
write <address> <value>	Attempt to write the given value to the address

Folder structure

This application has a different folder structure because it contains the firmware for CM4 and CM0+ applications as follows:

|-- proj_cm0p/           # CM0+ application folder
    |-- main.c
    |-- prot_units.c/h
    |-- Makefile
    |-- deps/            # All dependencies folder for CM0+
|-- proj_cm4/            # CM4 application folder
    |-- main.c
    |-- command_console  # Contains command console library
    |-- console.c/h
    |-- FreeRTOSConfig.h
    |-- Makefile
    |-- deps/            # All dependencies folder for CM4
|-- templates/           # Contains design configuration files shared between the CM0+ and CM4.
                                        # These files are replicated from the default BSP configuration.
                                        # This code example does not require any custom configuration.
                                        # The intent is to show how to share design configuration between the CM0+ and CM4.
                                        # Also contains linker scripts for the ARM/GCC_ARM/IAR toolchains for CM0P and CM4.

Linker script

When using the default BSP settings provided by the TARGET folder, it allocates only 8192 bytes of RAM and flash for the CM0+ CPU. This example requires more memory for CM0+; therefore, a custom linker script is required, which is located at templates/TARGET_/.

Some new sections are also added to the linker script to reflect the memory map shown in Figure 2.

Makefiles

The Makefiles for CM0+ and CM4 set the variable LINKER_SCRIPT to point to a custom linker script, based on the TOOLCHAIN and TARGET.

The CM0+ Makefile adds to the variable DEFINES the definition of CY_CORTEX_M4_APPL_ADDR, which is the CM4 application start address. This address must be manually set based on the location of the CM4 application. The CM0+ application uses this address to launch the CM4 application through the Cy_SysEnableCM4() function.

The CM4 application has a folder called command-console. The files from this folder come from this library. To avoid downloading unnecessary files, only the files related to the core command console are copied to the command-console folder.

Resources and settings

Table 1. Application resources

Resource	Alias/object	Purpose
UART (HAL)	cy_retarget_io_uart_obj	UART HAL object used by retarget i/o for printing to the console

Related resources

Resources	Links
Application notes	AN228571 – Getting started with PSoC™ 6 MCU on ModusToolbox™ software AN215656 – PSoC™ 6 MCU: Dual-CPU system design AN85951 – PSoC™ 4 and PSoC™ 6 MCU CAPSENSE™ design guide
Code examples	Using ModusToolbox™ software on GitHub Using PSoC™ Creator
Device documentation	PSoC™ 6 MCU datasheets PSoC™ 6 technical reference manuals
Development kits	Select your kits from the evaluation board finder
Libraries on GitHub	mtb-pdl-cat1 – PSoC™ 6 peripheral driver library (PDL) mtb-hal-cat1 – Hardware abstraction layer (HAL) library retarget-io – Utility library to retarget STDIO messages to a UART port
Middleware on GitHub	capsense – CAPSENSE™ library and documents psoc6-middleware – Links to all PSoC™ 6 MCU middleware
Tools	Eclipse IDE for ModusToolbox™ software – ModusToolbox™ software is a collection of easy-to-use software and tools enabling rapid development with Infineon MCUs, covering applications from embedded sense and control to wireless and cloud-connected systems using AIROC™ Wi-Fi and Bluetooth® connectivity devices. PSoC™ Creator – IDE for PSoC™ and FM0+ MCU development

Other resources

Infineon provides a wealth of data at www.infineon.com to help you select the right device, and quickly and effectively integrate it into your design.

For PSoC™ 6 MCU devices, see How to design with PSoC™ 6 MCU - KBA223067 in the Infineon community.

Document history

Document title: CE232321 - PSoC™ 6 MCU: Protection units

Version	Description of Change
1.0.0	New code example
1.1.0	Added target CYSBSYSKIT-DEV-01
1.2.0	Added support for target CY8CKIT-062S4
2.0.0	Major update to support ModusToolbox™ v3.0. This version is not backward compatible with previous versions of ModusToolbox™. Added support for 2 kits.

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