Electronics > FPGA

Newbie looking for advice on small glue logic in CPLD/FPGA/...


Hi, I need to put together a small microprocessor based controller that needs to be as small as possible, 5V based with some fairly complex external logic so I am thinking about a CMOS Programmable Logic Array (or such) that can be repeatably reprogrammed during development. I am probably talking about a 24 or max 32 pin package.

It would need maybe 10 latches and 20 gates.

I have considerable knowledge in electronics but not with these devices and want to gain some experience in using these, but the only thing is I am on a tight budget so free development and programming software is essential.

Advice on programming hardware (cheap) is also needed

Can anyone recommend a manufacturer/devices/programmer that meets this need ??

I am happy with github/sourceforge software or free manufacturers tools.


Have you looked at Cypress Psoc to integrate the logic and MCU?
Lattice XO2 may be an option. Note the Lattice CPLDs need software that is no longer free
If you really need 5V in & out, Atmel/Microchip ATV750 or ATV2500 might be worth a look.

You said "external" logic, but as mentioned above you might look at integrating the microcontroller with the logic in one device if that might be smaller in size and more convenient and maybe easier in some ways.

The PSOC suggestion above is a good one.  They had (when I last checked) some VERY nice low cost dev kits for PSOC4, PSOC5 and presumably possibly also PSOC3.

The PSOC4 devices can have a moderate number of UDBs (universal digital blocks) which may be enough to handle your logic.  Gates are usually not a problem.  Latches, like 1-bit latches?  That should be doable, too.  10 * 8-bit latches might be getting questionable.  The software (psoc creator) is free runs in Windows and is EASY to use.  Many parts are probably supportive of 5V IO, also, in those series.

On the other hand you could look at moving the microcontroller into a FPGA like the ones mentioned above, or maybe the ice40 or similar low cost FPGA series.  Or maybe something from altera or xilinx or other vendor if Lattice doesn't work for you.
The Lattice FPGA tools support a mico8 and mico32 soft-processor for free in devices that have enough logic to hold your design and the MCU IP core and such.  You usually don't get much internal flash ROM / RAM but maybe enough for you, or you can add external SPI FLASH for more ROM if you jump through the hoops to use it.

The Altera Intel MAX10 devices are nice and like all Intel FPGAs the tools support / include the free NIOS II/e microprocessor for the FPGA and software development integrated.  The MAX10 devices also include all the FLASH ROM you probably need for small / modest applications and something like the 10M08 might work for you in a very small system.  It isn't 5V IO though, I'm not sure if it is 5V tolerant for input (probably not).

I don't know how slow your logic is but you might even be able to use a standard MCU's function and GPIO pins to emulate gates and latches if they only have to operate below a few MHz speed.  A modern cheap MCU running at XX or XXX MHz can probably emulate some of those chips in firmware / electrically about the same speed as some old real 4000 series / TTL logic chips could operate.  If your logic is synchronous to some X MHz clock then maybe that could be synchronized with the MCU execution clock and the logic handled in a loop or IRQ routine.


--- Quote from: evb149 on June 11, 2021, 10:38:44 am ---You said "external" logic, but as mentioned above you might look at integrating the microcontroller with the logic in one device if that might be smaller in size and more convenient and maybe easier in some ways.
--- End quote ---
Absolutely, along with the PSOC some of the modern Microchip (Atmel) parts have programmable asynchronous "events" that provide rich interconnect between not just pins and hardware peripherals but also to/from LUTs and registers. Sadly not much in the way of 5V parts there either! Finding the right micro with the perfect matching capabilities is some what of a task, but probably easier than finding 5V programmable logic ;)

Too much logic for something like a GAL, but should easily fit inside a small CPLD. Unless you were ok with multiple GALs...

5V kind of limits the options. Altera and Xilinx had 5V products, but at least Altera doesn't produce them any more so you are stuck buying them second hand or new old stock if you are lucky enough. The EPM7000 series can be programmed in VHDL or Verilog and start from 32 macrocells in 44 pin packages.

Atmel has a current 5V product line in the ATF150x family of devices which you can still purchase new. They are so similar to the EPM7000 parts that you can translate the design from Altera to Atmel using a free tool. Alternatively you can use WinCUPL to design the logic.


[0] Message Index

There was an error while thanking
Go to full version