By Guest Author Bryan Fletcher, Avnet
In 2013, I was fortunate enough to help develop Avnet’s MicroZed system-on-module (SOM) board based on Xilinx’s Zynq™-7000 all-programmable system on a chip (SOC). This lower-cost platform is a great tool for evaluating Zynq for integration into your production application design.
After speaking with several Avnet customers over the last year about their specific project objectives, we developed a complementary SOM that is better-equipped to withstand the rugged conditions of industrial applications—and we call it the PicoZed.
While Avnet’s MicroZed and PicoZed boards both use quad SPI Flash—the fastest option for Zynq primary boot and well-supported in the Xilinx tools—quad SPI has limited capacity (128MB MAX for a single device). We overcame this limitation in the MicroZed platform by using a high-capacity microSD card, which can also be used as a primary boot source. But we found that SD cards present mechanical, temperature, and performance challenges for some industrial customers.
Xilinx’s Zynq SOC natively supports NAND Flash, but the Zynq NAND controller can’t natively manage the NAND for things like ECC, bad blocks, and wear leveling—leaving this management up to the developer. We decided that a managed NAND solution was the best option for high-capacity, non-volatile storage in Avnet’s PicoZed platform.
We selected a Micron e∙MMC device for PicoZed, which is a more rugged, soldered-down storage option than an SD card—with full industrial-temperature range options. And e∙MMC gives you the capacity of NAND without having to worry about the management. PicoZed includes 4GB by default but can be expanded up to 64GB. The maximum e∙MMC capacity is up to 512 times higher than the highest-capacity quad SPI NOR. The Zynq processing system (PS) MMC controller can support up to a x4 data path at a 52 MHz clock rate—meaning up to 26 MB/s, which is approximately 2.3 times better than a class-10 SD card.
The Zynq PS MMC controller cannot be used as a primary boot device, so we use a small quad SPI for primary boot (including fastest possible initial boot) in the PicoZed platform and then switch over to e∙MMC for secondary boot and mass storage. We think that Micron’s e∙MMC makes Avnet’s PicoZed a very compelling SOM option for many industrial applications. As far as I know, PicoZed is the only Zynq board available today with e∙MMC.
About Our Guest Blogger
Bryan Fletcher works on Avnet’s Global Technical Marketing team, where every team member has an electrical/computer engineering or computer science degree—so they are “heavy” on the technical part of technical marketing. His team is involved in the design, development, and production of Avnet’s development boards and SOMs, as well as the training programs offered for the boards, including the X-fest technical program. Bryan resides in Ephraim, Utah. He holds an AS from Snow College and a BSEE and MSEE from Utah State University.