Help selecting CPLD to use

Discussion in 'General Electronics Chat' started by El3ctroded, Nov 15, 2009.

  1. El3ctroded

    Thread Starter Active Member

    Feb 4, 2008
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    I want to look into the possibility of using a CPLD to increase options and decrease part count on a project, but am not sure what to choose, or what complexity of CPLD I will need.

    My primary concerns are:
    1) Cost of individual part $1 to $2 range
    2) Cost of design software Preferably Free or comes with an inexpensive demo board.

    My design consists of several basic logic chips such as AND and OR gates, and several 2 to 4 mux/demux chips such as the PI5C3253. Their main purpose are to serve for multiplexing my uart to multiple serial devices as well as the control of chip selects on other devices so I can free up mcu IO pins.

    I've looked around some and think an Altera Max 3000 would be a good place to start, but don't have the experience to know how much logic it can hold, or whether it can do what the PI5C3253 does (uses fets to allow bidirectional signals on the I/O pins).

    I've never used a CPLD, so am at a real loss as to where to start.

    Any help appreciated.
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,178
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    Based on your requirements

    1. I would start with locating the free tools.
    2. Then I would check distributor pricing on CPLDs to find one in the right price range.
    3. Then I would use the free tools to see if my application will fit in the device.
    4. Rinse and repeat steps 2-4 until success
    If you are on a tight schedule then something else will have to give.
     
  3. Thav

    Member

    Oct 13, 2009
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    Max II is a newer family from Altera with better density and it doesn't cost too much more. I'd suggest that, but MAX 3000 is a fine chip too.

    EDIT: Also if this is commercial, avoid the 3000, it may reach end of life soon.
     
  4. Papabravo

    Expert

    Feb 24, 2006
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    Great answer, except the price of a Max II is quite a bit North of $1-$2 even in the 100 pin TQFP. The BGA packages are certainly more expensive not to mention difficult to prototype with.

    At least at Digi-Key, Xilinx looks like the price leader for the parts. At least they have them in the $1-$2 range. Ahh..but the tools. They are not known for giving away the tools to sell chips, but I could be wrong.

    There is a 30 day evaluation on the download of ISE Design Suite. License cost for a node locked license for 1 year is $2995.00 on ISE Design suite : Logic Edition -- OUCH! Prices go up from there.

    Rotsa Ruck
     
    Last edited: Nov 16, 2009
  5. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
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    Both Xilinx and Altera offer free design software, the ISE Webpack and Quartis II, respectively. Make sure the parts you are considering are supported by the free software as they usually do not support 100% of the parts.
     
  6. Papabravo

    Expert

    Feb 24, 2006
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    Make sure you can do everything you need to do in 30 days.
     
  7. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
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    I haven't used them for a while now, they used to be free without a time restriction. I guess it is just one more thing to check before going forward...
     
  8. MaxSmoke

    Active Member

    Oct 29, 2009
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    I use Xilinx Webpack ISE and this tool is free with out a time limit. The larger chips in the Spartan family, like the XC3SD3400 DSP FPGA are not supported, but most Spartan FPGAs and CPLDs are supported by this software. This page on the Xilinx website shows a comparison.
    Design Tools

    You can design using primatives, but it is better if you can write in VHDL or Verilog. The even help by providing Verilog and VHDL templates. Take a look at the XC9536XL or the XC9572XL CPLDs. There are three speed flavours, 5ns, 7.5ns and 10ns.
     
  9. Papabravo

    Expert

    Feb 24, 2006
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    You seem to have found a winner. I guess it pays to read the fine print. I did not get the correct impression from a cursory look at the website. I got the distinct impression that every seat had to be licensed eventually. In that case I would make a list of the $1-$2 chips from the DigiKey website and have at it.
     
  10. MaxSmoke

    Active Member

    Oct 29, 2009
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    One point I should have mentioned is programming the CPLD. The normal way is to use in circuit programming, using the JTAG chain. This is a simple but very effect way to program the devices, and may be you are already aware of this method. However, to buy a Xilinx programming cable with leads, I think, is expensive for the amateur / hobbyist.

    Here a link Xilinx page that shows how to build you own parallel cable, using some 74HC125 tri-state buffers - JTAG Programmer. With this you should be able to use the Xilinx IMPACT tool that comes with the Free Xilinx Webpack ISE tools.

    There is a wealth of applications information on the Xilinx website, for example just search for CPLD Applications Handbook. Also, besides the XC9500 family I mentioned earlier, there is the low power CoolRunner family as well, but they may be more expensive. As Papabravo says you need to make a list of all the low cost CPLDs.

    Have Fun!
     
  11. El3ctroded

    Thread Starter Active Member

    Feb 4, 2008
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    Hey, thanks a lot everyone, and for that JTAG info MaxSmoke! Looks like Xilinx is the winner. One bad thing is that most are BGA or VQFP, but I found a PLCC one that likely will work.

    EDIT: Also, my laptop doesn't have anything but usb ports and I've learned the hard way that usb-to-serial and usb-to-parallel ports don't work very well for device programming... So I'm going to need a JTAG programmer with USB, unless someone has had successes with one. Also, I run Vista 64, so whatever I use Must support Vista 64-bit! Suggestions?
    EDIT2: found this usb jtag cable: http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,395,707&Prod=JTAG-USB-FS

    One thing no-one mentioned is whether or not the CPLDs can preform 3253 mux/demux functions?

    Thanks again
     
    Last edited: Nov 17, 2009
  12. MaxSmoke

    Active Member

    Oct 29, 2009
    35
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    The CPLD can perform the logic functions shown for the 74F253 / PI5C3253, in other words the truth-table, no problem. However, the CPLD does not contain transmission gates, so the 5Ω FETs in the PI5C3253 from input to out, cannot be implemented. But, this is not a problem if you are just looking to perform a straight forward logic Mux / Data Selection. Probably only use about two macrocells in the CPLD.
     
  13. El3ctroded

    Thread Starter Active Member

    Feb 4, 2008
    63
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    Actually I need 2 of each: mux and demux, but I guess they can be implemented separately. It sounds quite do-able with the selected chip: XC9536XL.

    Thanks again. I love learning new stuff :)
     
  14. ftsolutions

    Active Member

    Nov 21, 2009
    48
    2
    +1 for Xilinx ISE webpack and the 9536 or 9572 XL chips - you can fit a fair amount of useful stuff in there and the starter kits (used to be) quite reasonable. A good primer/start on using VHDL (or Verilog).
     
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