On May 13, 10:23*pm, Mike Harrison <m...@whitewing.co.uk> wrote:
> I'm looking at a possible application and trying to figure the relative costs of FPGA/CPLD versus
> MCU.
> I can do it with a microcontroller, but the only MCUs with the hardware Ineed (TFT LCD controller)
> tend to come with lots of other stuff (ethernet, large flash, USB etc.) which I don't need.

If you can find a chip that does the task, that's normally going to be
cheaper than a FPGA.
(even with unused bits )

Or, find a uC that is close, and add a smaller Prog Logic device to
stretch the peripherals.
Streaming SPI-CPLD can add quite smart 'external peripherals'.
The uC have Code-flash built in, as well as Analog features.

>
> As it can be hard to get 'real' prices of FPGAs without talking to all the distis etc. I *wonder if
> anyone can suggest parts to look at .
>
> Rough reqiurement is :
>
> Cheapest in 100x qtys for total solution inc. config and power supply ( from 3.3v supply), below
> about GBP5(US$7.5)
> Not BGA
> Readly available : ex-stock or sensible leadtimes (2 weeks)
> A couple of RAM blocks, around 1K byte each
> about 60 IOs, all 3.3v
> 30MHz clock
> Logic equivalent to around 100 CPLD macrocells
> Free or low cost (<$500) design software
>
> The Xilinx S3A/AN-50 is the cheapest I've found so far, but is a a bit over-specced.
> CPLDs seem to get expensive above 72 cells and don't tend to have RAM

The two choices do not really seem to overlap here ? - you have a
quite small logic block, and no
mention of any processor on the 2nd choice ?

100 macrocells is viable in CPLD (384/512 tend to not stack up), and a
device like
ATF1508RE (128MC 3.3V SingleSupply) is $3.90/100+ at Digikey.
You may be able to add SPI RAM - 32Kx8 is $1.09/100+