Mixed-signal FPGA

Posted January 4, 2006

Happy New Year!

To start off the new year, here's a nifty new family of chips: the Actel Fusion FPGA. Although they have some nice secondary features too, their killer characteristic is that they include some analog functionality, allowing a lot of secondary chips to be integrated right into the main FPGA.

Specifically, they have a nice multiplexing ADC with extensive prescaling options to read analog signals between -12 and +12V... the analog output feature is less interesting (where's the DAC?!), but does include some current-driving capabilities. If they wanted to really impress me, they'd have also shoved in some generic high-speed op-amps inside there as well, but as it is the chip is sane: they were, I think, mainly aiming for a system-monitor feature set, such as reading voltage and temperature measurements and adjusting fan speed, etc. For that sort of use, this is perfect, whereas personally I would be more interested in a comprehensive analog/digital signal processing chip, which would need more of an ability to compute with and output analog signals.

Some of the secondary features are neat too. The SRAM blocks include some extra circuitry to use them as FIFO queues with no user logic needed; pins can be assigned to different blocks for interfacing to chips running at different voltage levels; and most interestingly, there is a hardware AES encryption engine allowing the FPGA code to remain secret without a massive reverse-engineering effort... they even arranged it so that you can update the chip remotely with encrypted code over an untrusted channel like the internet. Nice!

Add a free IDE supporting Linux and a reasonably-priced ($350) hardware starter kit, and this looks like fun...