Electronics > FPGA

First FPGA project. Looking for advice

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hermitengineer:
This is my first time designing for an FPGA, and learning Verilog from zero.  So I'd appreciate any constructive criticism on coding, style, etc.  I developed the code in Vivado and simulated and synthesized it for an XC7S6 series chip to verify that it acts as it is supposed to.  It works (virtually) but uses maybe 5% of the chip's resources.

Second, this is a project to duplicate the functionality of a 40-pin DIP designed in the late 70's by General Instruments for an ancient game system.  As such, the board should also be about 40-pin DIP sized.  So, I'd also appreciate suggestions for an FPGA to use, along with the level shifters, voltage regulator(s), and flash memory.  Obviously, size would be the biggest issue.

Thanks

asmi:
You might want to take a look at Digilent's CMOD boards: CMOD A7 or CMOD S7. They have DIP-48 size, so not sure if it's going to be OK.

If you want to design your own, making it so small is going to be a challenge. The smallest package for S7 is 8x8 mm, but it's 0.5 mm ball pitch, so you will need to use advanced PCB tech. If you prefer to use more conventional tech, you can take a look at A7's CPG236/238 package (it's 0.5 mm pitch too, but the pinout is such that it's possible to route it using conventional PCB process) - it's 10x10 mm. The smallest "conventional PCB-friendly" S7 package is CSGA225, but at 13x13 mm it's probably a tad too close to the your size limits (assuming 0.7 inch or 17.8 mm for the PCB width). It could be doable though.

I think the XC7A12T-1CPG238 or XC7A15T-1CPG236 would be the best choice because they are the smallest accessible with conventional PCB tech. I've attached pinout diagrams and package drawing for A15T option for your convenience (taken from UG475), A12T has the same physical dimensions and footprint, but different pinout (see aforementioned user guide UG475 for all these details).

up8051:
It looks that your project is simple, maybe CPLD circuits will be enough.
For example: ATF150x 5V supply, PLCC44

woofy:
I did something similar for the Intel 4004 CPU, except I never needed the level shifting as it was a 3.3v replica from the start. But it did fit on a 16 pin DIP footprint. I used the Lattice ice40LP1k and GD25Q20C flash for that.
TheCP16xx (A PDP11 inspired device) is more complex so I would choose the ice40HX8k. The CB132 package will fit the 40 pin DIP footprint. A suitable flash could be the AT25SF081. Bidirectional 3.3v-5v level shifting could be done with TXS0108E devices. This will not take much power so linear regulators will be fine. You can ignore the 12v and -3v and just power from the 5v supply.

 

emece67:
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