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An ARM7-based SOC produced by Cirrus Logic. For the past few years, Cirrus Logic has sold quite a few EP7212 and EP7209 parts, thanks to their popularity in MP3 players. The top of the line processor used to be the EP7212, due to an interface to CD-quality audiophile grade DACs and an interface to DRAM. This combination proved perfect for rotating media MP3 players such as the Rio Volt and the Nomad Jukebox and network jukeboxes like the Turtle Beach Audiotron because the extra external memory proved necessary for buffering and deblocking the streaming data. Things were good. Then suddenly, as the memory market flooded with newer SDRAM components, the price of defunct EDO DRAM chips skyrocketed. To compensate for this market shift, the EP7312 was created.

The EP7312 is essentially an EP7212 with an SDRAM controller in place of the DRAM controller, a code encryption engine built on-chip, and an adjustable sample clock for the audio interface.

Other features of interest include:
  • ARM720T core
    • 74MHz core clock w/ 36MHz bus clock
    • 8kB four-way set associative cache
    • MMU with 64-entry TLB and optional write buffer
    • Embedded ICE debug support via JTAG interface
  • LCD display controller; compatible with greyscale LCDs and up to QVGA STN displays
  • 48kB on-chip SRAM useable as a framebuffer for the LCD or general purpose memory
  • DAI CD-quality audio codec supports up to 64kbps audio sample rates
  • 9.6Mbit SPI interface
  • dual 16550-style UARTs, one can drive an IrDA transceiver
  • JTAG boundary scan and embedded ICE support

There is a register that can be tweaked to make these puppies run at 92MHz, which eliminates an external clock necessary for the whole range of supported sample rates. In fact, I've seen these go as high as 110MHz in the lab. However, Cirrus Logic only guarantees the documented maximum tolerances at 74MHz.

One of the cool things about the EP7312 is that it is now available in a 13mmx13mm 204-ball TFBGA. You can, in fact, fit this part up your nose. This is what IBM used in the second revision of their Linux watch.

The design for the eval kit for the EP7312 has been outsourced to Cogent Computer Systems, Inc. The EDB7312 is encased in a small aluminum box with a color LCD and membrane keypad. This is contrary to the older eval kits which consisted of an open frame board on metal standoffs. This new eval kit is essentially idiot-proof, as there's nothing to short out or blow up unless you open it up to let out the signal goodness out. Nifty features include a built-in parallel port JTAG interface that emulates the Macraigor Wiggler, and IDE port, and an OpenFirmware monitor installed from the factory.

If you're wondering, the 'EDB' in EDB7312 stands for evaluation development board, not the other thing.

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