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Andy Peters
09/20/11 11:13
Read: 191 times
Tucson, Az
USA


 
#183816 - pedantry, again
Responding to: Richard Erlacher's previous message
Richard Erlacher said:
The one advantage of the CPLD over the FPGA, now making the distinction, is that, once programmed, the CPLD doesn't require it be programmed under system power each time the power is turned on.


There are some FPGA families which have onboard non-volatile configuration storage with "instant" configuration, meaning that as soon as power is stable the FPGA is configured. Actel's flash parts work this way. There are also OTP FPGAs (QuickLogic, Actel) which are also ready as soon as power is stable.

The real difference between a CPLD and an FPGA is that of resources. A CPLD macrocell has a much wider combinatorial logic resource in front of its (single) register than an FPGA's slice. An FPGA's slice may have one, two or even four registers and a simpler (3-, 4- or 6-input) combinatorial lookup table. FPGAs also have significantly greater routing resources than CPLDs, which is necessary if you need wide muxes and such.

Timing in a CPLD is simpler to analyze because the paths are simpler and delays fairly constant, but that's not really interesting any more since you do your FPGA design, set a clock period constraint, and let the tools have at it and they'll tell you if you win or not.

-a


List of 40 messages in thread
TopicAuthorDate
Bit-configurable transceiver chips        Per Westermark      09/12/11 02:28      
   Suggesting....again...      Michael Karas      09/12/11 05:35      
      Alas 5V needed and ribbon cables are a bit "rough"      Per Westermark      09/12/11 06:54      
   Another Suggestion....      Michael Karas      09/12/11 05:59      
   level translator      Jan Waclawek      09/12/11 06:21      
      Alas, "weak output drive" and no input hysterese      Per Westermark      09/12/11 07:30      
      TI sn74gtl2010      Stefan KAnev      09/17/11 02:18      
         or NXP GTL2010,GTL2000      Stefan KAnev      09/19/11 01:24      
            looks promising      Richard Erlacher      09/21/11 22:29      
            NXP GTL20xx -> NVT20xx      Jan Waclawek      10/04/11 00:57      
         Need to read more to understand them      Per Westermark      09/20/11 02:04      
            looks like the cat's miauw      Erik Malund      09/21/11 07:45      
   NXP has ....      Erik Malund      09/12/11 13:28      
      I2C or SPI just can't get even close to the huge bandwidth      Per Westermark      09/12/11 14:01      
         nope, no I²C clocks      Erik Malund      09/12/11 14:21      
            extender, not expander      Per Westermark      09/12/11 14:37      
   I have been wondering this myself      Justin Fontes      09/12/11 16:18      
      Supported capacitance seems to be the snag      Per Westermark      09/12/11 17:23      
   Differential SPI      Jez Smith      09/16/11 09:39      
      Serial -> buffers on adapter boards is a potential solution      Per Westermark      09/16/11 14:41      
   Have you considered programmable logic?      Richard Erlacher      09/19/11 14:08      
      I had suggested this as well      Michael Karas      09/19/11 14:33      
         Yes ... I remember that ...      Richard Erlacher      09/19/11 23:43      
            Long life      Per Westermark      09/20/11 01:59      
               They seem to live a long time ...      Richard Erlacher      09/20/11 09:22      
                  Adapters      Per Westermark      09/20/11 10:16      
                     These aren't necessarily so "huge"      Richard Erlacher      09/20/11 19:52      
                        Not huge in size      Per Westermark      09/21/11 01:49      
                           Some of them can handle that.      Richard Erlacher      09/21/11 22:34      
                              Yes and no      Per Westermark      09/22/11 04:53      
                                 There are ways ...      Richard Erlacher      09/22/11 10:55      
                                    Body diodes      Per Westermark      09/22/11 16:39      
                                       serial termination ...      Erik Malund      09/23/11 07:36      
                                          Yes, current- and bandwidth-limiting components used      Per Westermark      09/23/11 08:25      
                                             you youing whippersnappers, pay attention      Erik Malund      09/23/11 11:45      
            pedantry, again      Andy Peters      09/20/11 11:13      
               What would YOU suggest?      Richard Erlacher      09/20/11 19:45      
   Here's a thought ...      Richard Erlacher      10/17/11 03:03      
      Probably      Per Westermark      10/17/11 15:51      
         I'd sugest you consider older CPLD's      Richard Erlacher      10/17/11 19:14      

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