[Cryptech Tech] Selection of Lattice FPGA as key memory for the Alpha board

[Joachim Strömbergson]

Aloha!

(Lets do this on @tech. Hopefully somebody else want to chime in with
suggestions and ideas.)

Pavel, I’ve looked at possible FPGA devices to be integrated onto the
new Cryptech board to be used as FPGA based master key memory
(fpga_mkm). Here are my reasoning for the devices I’ve selected.

We want to use a device supported by the Project IceStorm toolchain:
[Project IceStorm"](http://www.clifford.at/icestorm/). The toolchain
supports a number of devices in the iCE40 LP/HX/LM series:
https://www.latticesemi.com/Products/FPGAandCPLD/iCE40

We are currently using the iCEstick evaluation board for the
development. The iCEstick is supported by the toolchain. [iCEstick
Evaluation Kit - Lattice
Semiconductor](http://www.latticesemi.com/en/Products/DevelopmentBoardsAndKits/iCEstick).

The dev board sports a iCE40HX1K device. Judging by resource numbers we
are currently using 15% of the Programmable Logic Blocks. This means
that we could use a smaller device. But the 1K-devices contain an PLL
that can be used as clock source (meaning no external clock). I would
therefore suggest that we choose one of the 1K-devices.

We also need very few I/Os. We currently use nine I/Os, and one is for
clock and two are just for debugging (red and green LEDs)

Based on this, and looking at availability, I have the following LP1L
devices on my list:

* [ICE40LP1K-SWG16TR Lattice Semiconductor Corporation | Integrated
Circuits (ICs) |
DigiKey](https://www.digikey.com/product-detail/en/lattice-semiconductor-corporation/ICE40LP1K-SWG16TR/ICE40LP1K-SWG16TR-ND/4572398).

* [ICE40LP1K-CM36 Lattice Semiconductor Corporation | Integrated
Circuits (ICs) |
DigiKey](https://www.digikey.com/product-detail/en/lattice-semiconductor-corporation/ICE40LP1K-CM36/220-1564-ND/3083574)

The 16-ball WLCSP has 0.35 mm spacing and the 36-ball ucBGA has 0.40 mm
spacing.

From LM1K I would suggest:
* [ICE40LM1K-SWG25TR Lattice Semiconductor Corporation | Integrated
Circuits (ICs) |
DigiKey](https://www.digikey.com/product-detail/en/lattice-semiconductor-corporation/ICE40LM1K-SWG25TR/ICE40LM1K-SWG25TR-ND/4572404)

The 25-ball WLCSP has 0.35 mm spacing.

All devices seems to be in active production and accessible in single
quantities for around 3 USD. Do you think any of these would work?
Anyone that you prefer?

I haven’t looked at how we are going to program the devices on the
board. The devices contain a Flash based config memory that can be
programmed and then locked. This is a feature we want to use.

-- 
Med vänlig hälsning, Yours

Joachim Strömbergson
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                               Assured AB
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