Tag Archives: SAM V71

6 memory considerations for Cortex-M7-based IoT designs

Taking a closer look at the configurable memory aspects of Cortex-M7 microcontrollers.

Tightly coupled memory (TCM) is a salient feature in the Cortex-M7 lineup as it boosts the MCU’s performance by offering single cycle access for the CPU and by securing the high-priority latency-critical requests from the peripherals.


The early MCU implementations based on the ARM’s M7 embedded processor core — like Atmel’s SAM E70 and S70 chips — have arrived in the market. So it’d be worthwhile to have a closer look at the configurable memory aspects of M7 microcontrollers and see how the TCMs enable the execution of deterministic code and fast transfer of real-time data at the full processor speed.

Here are some of the key findings regarding the advanced memory architecture of Cortex-M7 microcontrollers:

1. TCM is Configurable

First and foremost, the size of TCM is configurable. TCM, which is part of the physical memory map of the MCU, supports up to 16MB of tightly coupled memory. The configurability of the ARM Cortex-M7 core allows SoC architects to integrate a range of cache sizes. So that industrial and Internet of Things product developers can determine the amount of critical code and real-time data in TCM to meet the needs of the target application.

The Atmel | SMART Cortex-M7 architecture doesn’t specify what type of memory or how much memory should be provided; instead, it leaves these decisions to designers implementing M7 in a microcontroller as a venue for differentiation. Consequently, a flexible memory system can be optimized for performance, determinism and low latency, and thus can be tuned to specific application requirements.

2. Instruction TCM

Instruction TCM or ITCM implements critical code with deterministic execution for real-time processing applications such as audio encoding/decoding, audio processing and motor control. The use of standard memory will lead to delays due to cache misses and interrupts, and therefore will hamper the deterministic timing required for real-time response and seamless audio and video performance.

The deterministic critical software routines should be loaded in a 64-bit instruction memory port (ITCM) that supports dual-issue processor architecture and provide single-cycle access for the CPU to boost MCU performance. However, developers need to carefully calibrate the amount of code that need zero-wait execution performance to determine the amount of ITCM required in an MCU device.

The anatomy of TCM inside the M7 architecture

The anatomy of TCM inside the M7 architecture.

3. Data TCM

Data TCM or DTCM is used in fast data processing tasks like 2D bar decoding and fingerprint and voice recognition. There are two data ports (DTCMs) that provide simultaneous and parallel 32-bit data accesses to real-time data. Both instruction TCM and data TCM — used for efficient access to on-chip Flash and external resources — must have the same size.

4. System RAM and TCM

System RAM, also known as general RAM, is employed for communications stacks related to networking, field buss, high-bandwidth bridging, USB, etc. It implements peripheral data buffers generally through direct memory access (DMA) engines and can be accessed by masters without CPU intervention.

Here, product developers must remember the memory access conflicts that arise from the concurrent data transfer to both CPU and DMA. So developers must set clear priorities for latency-critical requests from the peripherals and carefully plan latency-critical data transfers like the transfer of a USB descriptor or a slow data rate peripheral with a small local buffer. Access from the DMA and the caches are generally burst to consecutive addresses to optimize system performance.

It’s worth noting that while system memory is logically separate from the TCM, microcontroller suppliers like Atmel are incorporating TCM and system RAM in a single SRAM block. That lets IoT developers share general-purpose tasks while splitting TCM and system RAM functions for specific use cases.

A single SRAM block for TCM and system memory allows higher flexibility and utilization

A single SRAM block for TCM and system memory allows higher flexibility and utilization.

5. TCM Loading

The Cortex-M7 uses a scattered RAM architecture to allow the MCU to maximize performance by having a dedicated RAM part for critical tasks and data transfer. The TCM might be loaded from a number of sources, and these sources aren’t specified in the M7 architecture. It’s left to the MCU designers whether there is a single DMA or several data loading points from various streams like USB and video.

It’s imperative that, during the software build, IoT product developers identify which code segments and data blocks are allocated to the TCM. This is done by embedding programs into the software and by applying linker settings so that software build appropriately places the code in memory allocation.

6. Why SRAM?

Flash memory can be attached to a TCM interface, but the Flash cannot run at the processor clock speed and will require caching. As a result, this will cause delays when cache misses occur, threatening the deterministic value proposition of the TCM technology.

DRAM technology is a theoretical choice but it’s cost prohibitive. That leaves SRAM as a viable candidate for fast, direct and uncached TCM access. SRAM can be easily embedded on a chip and permits random accesses at the speed of the processor. However, cost-per-bit of SRAM is higher than Flash and DRAM, which means it’s critical to keep the size of the TCM limited.

Atmel | SMART Cortex-M7 MCUs

Take the case of Atmel’s SMART SAM E70, S70 and V70/71 microcontrollers that organize SRAM into four memory banks for TCM and System SRAM parts. The company has recently started shipping volume units of its SAM E70 and S70 families for the IoT and industrial markets, and claims that these MCUs provide 50 percent better performance than the closest competitor.


Atmel’s M7-based microcontrollers offer up to 384KB of embedded SRAM that is configurable as TCM or system memory for providing IoT designs with higher flexibility and utilization. For instance, E70 and S70 microcontrollers organize 384KB of embedded SRAM into four ports to limit memory access conflicts. These MCUs allocate 256KB of SRAM for TCM functions — 128 KB for ITCM and DTCM each — to deliver zero wait access at 300MHz processor speed, while the remaining 128KB of SRAM can be configured as system memory running at 150MHz.

However, the availability of an SRAM block organized in the form of a memory bank of 384KB means that both system SRAM and TCM can be used at the same time.The large on-chip SRAM of 384KB is also critical for many IoT devices, since it enables them to run multiple communication stacks and applications on the same MCU without adding external memory. That’s a significant value proposition in the IoT realm because avoiding external memories lowers the BOM cost, reduces the PCB footprint and eliminates the complexity in the high-speed PCB design.

3 design hooks of Atmel MCUs for connected cars

The MPU and MCU worlds are constantly converging and colliding, and the difference between them is not a mere on-off switch — it’s more of a sliding bar. 

In February 2015, BMW reported that it patched the security flaw which could allow hackers to remotely unlock the doors of more than 2 million BMW, Mini and Rolls-Royce vehicles. Earlier, researchers at ADAC, a German motorist association, had demonstrated how they could intercept communications with BMW’s ConnectedDrive telematics service and unlock the doors.


BMW uses SIM card installed in the car to connect to a smartphone app over the Internet. Here, the ADAC researchers created a fake mobile network and tricked nearby cars into taking commands by reverse engineering the BMW’s telematics software.

The BMW hacking episode was a rude awakening for the connected car movement. The fact that prominent features like advanced driver assistance systems (ADAS) are all about safety and security is also a testament is that secure connectivity will be a prime consideration for the Internet of Cars.

Built-in Security

Atmel is confident that it can establish secure connections for the vehicles by merging its security expertise with performance and low-power gains of ARM Cortex-M7 microcontrollers. The San Jose, California-based chip supplier claims to have launched the industry’s first auto-qualified M7-based MCUs with Ethernet AVB and media LB peripherals. In addition, this high-end MCU series for in-vehicle infotainment offers the CAN 2.0 and CAN flexible data rate controller for higher bandwidth requirements.

Nicolas Schieli, Automotive MCU Marketing Director at Atmel, acknowledges that security is something new in the automotive environment that needs to be tackled as cars become more connected. “Anything can connect to the controller area network (CAN) data links.”

Schieli notes that the Cotex-M7 has embedded enhanced security features within its architecture and scalability. On top of that, Atmel is using its years of expertise in Trusted Platform Modules and crypto memories to securely connect cars to the Internet, not to mention the on-chip SHA and AES crypto engines in SAM E70/V70/V71 microcontrollers for encryption of data streams. “These built-in security features accelerate authentication of both firmware and applications.”


Schieli notes that the Cotex-M7 has embedded enhanced security features within its architecture and scalability. On top of that, Atmel is using its years of expertise in Trusted Platform Modules and crypto memories to securely connect cars to the Internet, not to mention the on-chip SHA and AES crypto engines in SAM E70/V70/V71 microcontrollers for encryption of data streams. “These built-in security features accelerate authentication of both firmware and applications.”

He explained how the access to the Flash, SRAM, core registers and internal peripherals is blocked to enable security. It’s done either through the SW-DP/JTAG-DP interface or the Fast Flash Programming Interface. The automotive-qualified SAM V70 and V71 microcontrollers support Ethernet AVB and Media LB standards, and they are targeted for in-vehicle infotainment connectivity, audio amplifiers, telematics and head control units companion devices.

Software Support

The second major advantage that Atmel boasts in the connected car environment is software expertise and an ecosystem to support infotainment applications. For instance, a complete automotive Ethernet Audio Video Bridging (AVB) stack is being ported to the SAM V71 microcontrollers.

Software support is a key leverage in highly fragmented markets like automotive electronics. Atmel’s software package encompasses peripheral drivers, open-source middleware and real-time operating system (RTOS) features. The middleware features include USB class drivers, Ethernet stacks, storage file systems and JPEG encoder and decoder.

Next, the company offers support for several RTOS platforms like RTX, embOS, Thread-X, FreeRTOS and NuttX. Atmel also facilitates the software porting of any proprietary or commercial RTOS and middleware. Moreover, the MCU supplier from San Jose features support for specific automotive software such as AUTOSAR and Ethernet AVB stacks.

Atmel supports IDEs such as IAR or ARM MDK and Atmel Studio and it provides a full-featured board that covers all MCU series, including E70, V70 and V71 devices. And, a single board can cover all Atmel microcontrollers. Moreover, the MCU supplier provides Board Support Package for Xplained evaluation kit and easy porting to customer boards through board definition file (board.h).

Beyond that, Atmel is packing more functionality and software features into its M7 microcontrollers. Take SAM V71 devices, for example, which have three software-selectable low-power modes: sleep, wait and backup. In sleep mode, the processor is stopped while all other functions can be kept running. While in wait mode, all clocks and functions are stopped but some peripherals can be configured to wake up the system based on predefined conditions. In backup mode, RTT, RTC and wake-up logic are running. Furthermore, the microcontroller can meet the most stringent key-off requirements while retaining 1Kbyte of SRAM and wake-up on CAN.

Transition from MPU to MCU

Cortex-M7 is pushing the microcontroller performance in the realm of microprocessors. MPUs, which boast memory management unit and can run operating systems like Linux, eventually lead to higher memory costs. “Automakers and systems integrators are increasingly challenged in getting performance point breakthrough because they are running out of Flash capacity,” explained Schieli.

On the other hand, automotive OEMs are trying to squeeze costs in order to bring the connected car riches to non-luxury vehicles, and here M7 microcontrollers can help bring down costs and improve the simplification of car connectivity.

The M7 microcontrollers enable automotive embedded systems without the requirement of a Linux head and can target applications with high performance while running RTOS or bare metal implementation. In other words, M7 opens up avenues for automotive OEMs if they want to make a transition from MPU to MCU for cost benefits.

However, the MPU and MCU worlds are constantly converging and colliding, and the difference between them is not a mere on-off switch. It’s more of a sliding bar. Atmel, having worked on both sides of the fence, can help hardware developers to manage that sliding bar well. “Atmel is using M7 architecture to help bridge the gap between microprocessors and high-end MCUs,” Schieli concludes.

Majeed Ahmad is the author of books Smartphone: Mobile Revolution at the Crossroads of Communications, Computing and Consumer Electronics and The Next Web of 50 Billion Devices: Mobile Internet’s Past, Present and Future.

Atmel tightens automotive focus with new Cortex-M7 MCUs

Large SoCs without an Ethernet interface typically have slow start-up times and high-power requirements — until now. 

Atmel, a lead partner for the ARM Cortex-M7 processor launch in October 2014, has unveiled three new M7-based microcontrollers with a unique memory architecture and advanced connectivity features for the connected car market.

According to a company spokesman, E70, V71 and V70 chips are the industry’s highest performing Cortex-M microcontrollers with six-stage dual-issue pipeline delivering 1500 CoreMarks at 300MHz. Moreover, V70 and V71 microcontrollers are the only automotive-qualified ARM Cortex-M7 MCUs with Audio Video Bridging (AVB) over Ethernet and Media LB peripheral support.


Atmel is among the first suppliers to introduce the ARM Cortex-M7-based MCUs, whose core combines performance and simplicity and further pushes the performance envelope for embedded devices. The new MCU devices are aimed to take the connected car design to the next performance level with high-speed connectivity, high-density on-chip memory, and a solid ecosystem of design engineering tools.

Atmel’s Memory Play

Atmel has memory technology in its DNA, and that seems apparent in the design footprint of E70, V70 and V71 MCUs. The San Jose-based chipmaker is offering a flexible memory system that is optimized for performance, determinism and low latency.

Jacko Wilbrink, Senior Marketing Director at Atmel, said that the company’s Cortex-M7-based MCUs leverage Atmel’s advanced peripherals and flexible SRAM architecture for higher performance applications while keeping the Cortex-M class ease-of-use. He added that the large on-chip SRAM on SAM E70/V70/V71 chips is critical for connected car and IoT product designers since it allows them to run the multiple communication stacks and applications on the same MCU without adding external memory.

On-chip DMA and low-latency access SRAM architecture

On-chip DMA and low-latency access SRAM architecture

Avoiding the external memories reduces the PCB footprint, lowers the BOM cost and eliminates the complexity of high-speed PCB design when pushing the performance to a maximum. Next, Tim Grai, another senior manager at Atmel, pointed out another critical take from Cortex-M7 designs: The tightly coupled memory (TCM) interface. It provides the low-latency memory that the processor can use without the unpredictability that is a feature of cache memories.

Grai says that the most vital memory feature is not the memory itself but how the TCM interface to the M7 is utilized. “The available RAM is configurable to be used as system RAM or tightly-coupled instruction and data memory to the core, where it provides deterministic zero-wait state access,” Grai added. “The arrangement of SRAM allows for multiple concurrent accesses.”

Cortex-M7 a DSP Winner

According to Will Strauss, President & Principal Analyst at Forward Concepts, ARM has had considerable success with its Cortex-M4 power-efficient 32-bit processor chip family. “However, realizing that it lacked the math ability to do more sophisticated DSP functions, ARM has introduced the Cortex-M7, its newest and most powerful member of the Cortex-M family.”

Strauss adds that the M7 provides 32-bit floating point DSP capability as well as faster execution times. With the greater clock speed, floating point and twice the DSP power of the M4, the M7 is even more attractive for applications requiring high-performance audio and even video accompanying traditional automotive and control applications.

Atmel’s Grai added an interesting dimension to the DSP story in Cortex-M7 processor fabric. He pointed out that true DSPs don’t do control and logical functions well and generally lack the breadth of peripherals available on MCUs. “The attraction of the M7 is that it does both—DSP functions and control functions—hence it can be classified as a digital signal controller (DSC).”

Grai quoted the example of Atmel V70 and V71 microcontrollers used to connect end-nodes like infotainment audio amplifiers to the emerging Ethernet AVB network. In an audio amplifier, you receive a specific audio format that has to be converted, filtered, modulated to match the requirement for each specific speaker in the car. So you need Ethernet and DSP capabilities at the same time.

Grai says that the audio amplifier in infotainment applications is a good example of DSC: a mix of MCU capabilities and peripherals plus DSP capability for audio processing. Atmel is targeting the V70 and V71 chips as a bridge between large application processors and Ethernet.

Most of the time, the main processor does not integrate Ethernet AVB, as the infotainment connectivity is based on Ethernet standard. Here, the V71 microcontroller brings this feature to the main processor. “Large SoCs, which usually don’t have Ethernet interface, have slow start-up time and high power requirements,” Grai said. “Atmel’s V7x MCUs allow fast network start-up and facilitate power moding.”

The SAM E70, V70 and V71

Atmel’s three new MCU devices are aimed at multiple aspects of in-vehicle infotainment connectivity and telematics control.

SAM E70: The microcontroller series features Dual CAN-FD, 10/100 Ethernet MAC with IEEE1588 real-time stamping, and AVB support. It’s aimed at automotive industry’s movement toward controller area network (CAN) message-based protocols holistically across the cabin, eliminating isolation and wire redundancy, and have them all bridged centrally with the CAN interface.

SAM V70: It’s designed for MediaLB connectivity and leverages advanced audio processing, multi-port memory architecture and Cortex-M7 DSP capabilities. For the media-oriented systems transport (MOST) architecture, old modules are not redesigned. So Atmel offers a MOST solution that is done over Media Local Bus (MediaLB) and is supported by the V70 series.

SAM V71: The MCU series ports a complete automotive Ethernet AVB stack for in-vehicle infotainment connectivity, audio amplifiers, telematics and head control units. It mirrors the SAM V70 series features as well as combines Ethernet-AVB and MediaLB connectivity stacks.

Majeed Ahmad is the author of books Smartphone: Mobile Revolution at the Crossroads of Communications, Computing and Consumer Electronics and The Next Web of 50 Billion Devices: Mobile Internet’s Past, Present and Future.

Single chip MCU + DSP architecture for automotive = SAM V71

Automotive apps are running in production by million units per year, and cost is a crucial factor when deciding on an integrated solution.

It’s all about Cost of Ownership (CoO) and system level integration. If you target automotive related application, like audio or video processing or control of systems (Motor control, inverter, etc.), you need to integrate strong performance capable MCU with a DSP. In fact, if you expect your system to support Audio Video Bridging (AVB) MAC on top of the targeted application and to get the automotive qualification, the ARM Cortex-M7 processor-based Atmel SAMV70/71 should be your selection: offering the fastest clock speed of his kind (300 MHz), integrating a DSP Floating Point Unit (FPU), supporting AVB and qualified for automotive.

Let’s have a closer look at the SAM V71 internal architecture, shall we?

A closer look at Atmel | SMART ARM based Cortex M7 - SAMV71 internal architecture.

A closer look at Atmel | SMART ARM based Cortex M7 – SAMV71 internal architecture.

When developing a system around a microcontroller unit, you expect this single chip to support as many peripherals as needed in your application to minimize the global cost of ownership. That’s why you can see the long list of system peripherals (top left of the block diagram). Meanwhile, the Atmel | SMART SAM V71 is dedicated to support automotive infotainment application, e.g. Dual CAN and Ethernet MAC (bottom right). If we delve deeper into these functions, we can list these supported features:

  • 10/100 Mbps, IEEE1588 support
  • MII (144-pin), RMII (64-, 100, 144-pin)
  • 12 KB SRAM plus DMA
  • AVB support with Qav & Qas HW support for Audio traffic support
  • 802.3az Energy efficiency support
  • Dual CAN-FD
  • Up to 64 SRAM-based mailboxes
  • Wake up from sleep or wake up modes on RX/TX

The automotive-qualified SAM V70 and V71 series also offers high-speed USB with integrated PHY and Media LB, which when combined with the Cortex-M7 DSP extensions, make the family ideal for infotainment connectivity and audio applications. Let’s take a look at this DSP benchmark:

DSP bench-Atmel-SAM-Cortex-M7

ARM CM7 Performance normalized relative to SHARC (Higher numbers are better).

If you are not limited by budget consideration and can afford integrating one standard DSP along with a MCU, you will probably select the SHARC 21489 DSP (from Analog Devices) offering the best-in-class benchmark results for FIR, Biquad and real FFT. However, such performance has a cost, not only monetarily but also in terms of power consumption and board footprint — we can call that “Cost of Ownership.” Automotive apps are running in production by million units per year, and cost is absolutely crucial in this market segment, especially when quickly deciding to go with an integrated solution.

To support audio or video infotainment application, you expect the DSP integrated in the Cortex-M7 to be “good enough” and you can see from this benchmark results that it’s the case for Biquad for example, as ARM CM7 is equal or better than any other DSP (TI C28, Blackfin 50x or 70x) except the SHARC 21489… but much cheaper! Good enough means that the SAMV70 will support automotive audio (Biquad in this case) and keep enough DSP power for Ethernet MAC (10/100 Mbps, IEEE1588) support.

Ethernet AVB via Atmel Cortex M7

Ethernet AVB Architectures (SAM V71)

In the picture above, you can see the logical SAM V71 architectures for Ethernet AVB support and how to use the DSP capabilities for Telematics Control Unit (TCU) or audio amplifier.

Integrating a DSP means that you need to develop the related DSP code. Because the DSP is tightly integrated into the ARM CM7 core, you may use the MCU development tools (and not specific DSP tools) for developing your code. Since February, the ATSAMV71-XULT (full-featured Xplained board, SAM V71 Xplained Ultra Evaluation Kit with software package drivers supporting basic drivers, software services, libraries for Atmel SAMV71, V70, E70, S70 Cortex-M7 based microcontrollers) is available from Atmel. As this board has been built around the feature-rich SAM V71, you can develop your automotive application on the same exact MCU architecture as the part going into production.

SAMV71 Ultra Xplained - Atmel ARM Cortex M7

Versatility and Integrated DSP built into the ARM CM7 core allows for MCU development tools to be used instead of having to revert to specific DSP tools. You can develop your automotive application on exactly the same MCU architecture than the part going into production.

Interested? More information on this eval/dev board can found here.

This post has been republished with permission from SemiWiki.com, where Eric Esteve is a principle blogger as well as one of the four founding members of SemiWiki.com. This blog first appeared on SemiWiki on April 29, 2015.