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Asymmetrical Multicore SoC Services Automotive Applications

Freescale is a major supplier of automotive micros. Its new Vybrid VF series bring asymmetrical multicore services to automotive applications. It targets in-vehicle applications that might run on Linux platforms like those targeted by the Genivi Alliance.

The Vybrid architecture (Fig. 1) blends the 32-bit Cortex-A5 and the Cortex-M4 from Arm. Vybrid is not the first mixed core platform. NXP's LPC4000 (see New Platform Approaches Deliver Top Digital Designs In 2010) mixes a Cortex-M4 with a smaller Cortex-M0. Arm's big.LITTLE architecture blends a Cortex-A7 and Cortex-A15 (see Little Core Shares Big Core Architecture) NVidia's Tegra 3 powers Google's 7-in Nexus 7 tablet (see iFixit Tears Down The Google Nexus 7 Tablet). The quad core Cortex-A9 platform has a fifth, low power Cortex core in addition to a 12-core NVidia GPU.


Figure 1. Freescale's Vybrid microcontroller series pairs an Arm Cortex-A5 with a Cortex-M4.

The VF series features up to 1.5 Mbytes of on-chip SRAM with ECC (error correction code) support. The DDR3/LPDDR2 controller and NAND flash controller also has ECC support. ECC is important for critical applications such as automotive. It is also combined with secure boot using cryptography algorithm hardware acceleration and tamper detection support to prevent malicious or accidental changes from affecting the operation of the platform.

The VF series is not designed for the engine control unit (ECU). Freescale's multicore Qorivva line includes the three core MPC5746M (see Three Core Micro Pushes Powertrain Performance) that runs a pair of Power cores in lockstep and adds a peripheral processor to the mix.

Still, security and reliability are still important because safety related design criteria is at the top of the list for that LCD display sitting between the driver and passenger. A corrupt or improperly designed application can easily distract the driver.

The VF series chips also includ a pair of quad-SPI interfaces with double-data-rate capability. This allows execute-in-place (XIP) code using quad-SPI serial memory chips. There are two Ethernet controllers with an level 2 (L2) switch. Two USB 2.0 OTG ports have integrated, high-speed PHYs. There is a mix of CAN, UART and I2C interfaces as well.

The real-time I/O subsystem incorporates pulse-width modulation (PWM) timing system, two 12-bit analog-to-digital converters (ADCs) and a pair of 12-bit digital-to-analog converters (DACs). There are multiple audio interfaces included as well.

Displays can be driven by the OpenVG graphics processing unit (GPU). The dual display controllers also have a video/camera interface.

Automotive applications are the target for the VF series but it will also be available for Freescale's Tower development platform. MQX RTOS is supported by Freescale (see Prototyping A Tower) for the Tower. The VF series also has support for a range of third party development tool and RTOS software.

Developers can easily move code from one core to another although it is clear that the Cortex-M4 will be handling audio chores. Its DSP support is great for timing related chores. The Cortex-A5 will probably handle user interface and network support. This heftier core can handle Linux. Wireless support can be handle by a range of interfaces including SPI. The USB OTG and Ethernet can provide user access to the system.

Freescale expects the Vybrid VF series to be around awhile. They will be supported by Freescale's product longevity program so chips will be available for a minimum of 10 years.

Vybrid will definitely be a factor in automotive applications but it will be interesting to see if it finds a home in other application areas.

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