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Electronics Forum / Basics / September 2006Logic equivalent in electronic
HI, I am trying to find if there is an equivalent in electronic (most probably digital) for some common programming language. What would be the equivalent of 'if - then' , 'else' etc... I am builing a digial circuits with inverters , Nand gates etc.. but would like to implement more complex decision. I did not find anything on google, does anybody know about these pre-made circuitry? thank you ken > I am trying to find if there is an equivalent in electronic (most > probably digital) for some common programming language. [quoted text clipped - 3 lines] > I did not find anything on google, does anybody know about these > pre-made circuitry? If...else is trivial: (view with fixed-width font) if -------+-------------- then | | |\ | | \ +--| >O------- else | / |/ If you want to learn how to do logic which depends on past as well as present input (logic with memory) do a search on "sequential logic". You'll learn about flip-flops, clocks, counters... Tim >HI, > >I am trying to find if there is an equivalent in electronic (most >probably digital) for some common programming language. >What would be the equivalent of 'if - then' , 'else' etc... --- In order to implement the statement: "If 'W', then 'O' = 'X', else 'O' = 'Y' you could do this: (view in Courier) W>-----+-------A | NAND Y--+ X>-----|-------B | | +--A [INV] NAND Y--->O | +--B +-------A | NAND Y--+ Y>-------------B --- >I am builing a digial circuits with inverters , Nand gates etc.. but >would like to implement more complex decision. >I did not find anything on google, does anybody know about these >pre-made circuitry? --- How do you mean "pre-made?"  SignatureJohn Fields Professional Circuit Designer > >HI, > > [quoted text clipped - 25 lines] > --- > How do you mean "pre-made?" Thanks a lot, no I have something to start with . I just meant by pre-made that maybe there is a chip that would include al those NAND and inverters. Ken >> >HI, >> > [quoted text clipped - 31 lines] > > Ken Hi all, I'm a "newbie" too...at least in the advanced world of digital. But wouldn't PLC's be what the OP is refering to when he inquires about a chip with "all those" gates? 'Sorry if I don't sound like I know what I'm talking about, but I'm still trying to figure it out myself. Regards, Scott To see how complex this topic is and the number of devices that are available to perform programmable logic look at this chart. http://i.cmpnet.com/pldesignline/2006/07/compuniverse-lg.gif Below Source http://www.bit7.com/whitepage/FPGA/fpgaone.htm A programmable logic device (PLD, also referred to as a PAL, PLA, CPLD or FPGA among others) is essentially a collection of general purpose digital circuitry and interconnection resources. The design process for a PLD results in a specification of how those resources are configured and connected together to implement the desired circuit. Rather than select different components and physically connect them to get the desired circuit behavior, the engineer can add a PLD to the circuit and implement all the required logic circuitry in the PLD with greater ease and flexibility. Applications The spectrum of programmable logic parts runs from simple 16 pin PALs suitable for replacing a few logic gates to multi-million gate, thousand pin FPGAs capable of implementing complex data processing functions or special purpose microprocessors. A typical small application might be to replace several logic gates spread among a few chips in a design with a single chip programmed to perform the same functions. These include address decoding, glue logic or simple signal generators. More involved circuits might include sequence controllers, state machines etc. Large applications may include interface control blocks (e.g. PCI bus, DVI), arithmetic processing or other data processing. Microcontrollers can also be included in FPGAs which, with the addition of controlling software, can result in complete, highly specialized designs in a single chip. FPGAs are also used to prototype microcontrollers, microprocessors and other designs intended for implementation in ASICs. > To see how complex this topic is and the number of devices that are > available to perform programmable logic look at this chart. [quoted text clipped - 16 lines] > > The spectrum of programmable logic parts runs from simple 16 pin PALs And now GALs of course. Same concept different implementation. > suitable for replacing a few logic gates to multi-million gate, > thousand pin FPGAs capable of implementing complex data processing [quoted text clipped - 12 lines] > single chip. FPGAs are also used to prototype microcontrollers, > microprocessors and other designs intended for implementation in ASICs. I came across an interesting use of FPGAs online which is to implement a VGA controller. Whilst such a thing is of little interest to the PC community anymore it continues to be of interest to those ppl designing embedded electronics and since the usual chipsets vanshed a 'replacement' was needed. See also. http://en.wikipedia.org/wiki/Programmable_Array_Logic http://en.wikipedia.org/wiki/Programmable_logic_device Graham > To see how complex this topic is and the number of devices that are > available to perform programmable logic look at this chart. [quoted text clipped - 32 lines] > single chip. FPGAs are also used to prototype microcontrollers, > microprocessors and other designs intended for implementation in ASICs. Leslie, Thanks for the link. Wow! Pretty big picture for devices. I'm reviewing (auditing) my digital stuff right now, and hopefully moving on to FPGA's, etc... That site has been helpful in my understanding of the bigger picture. Scott > "lerameur" <lerameur@yahoo.com> wrote in message > >> [quoted text clipped - 34 lines] > those" gates? 'Sorry if I don't sound like I know what I'm talking about, > but I'm still trying to figure it out myself. Programmable logic controllers go a bit further still. Graham > > >HI, > > > [quoted text clipped - 29 lines] > I just meant by pre-made that maybe there is a chip that would include > al those NAND and inverters. GALs ( generic array logic ). Graham >> > >HI, >> > > [quoted text clipped - 33 lines] > >Graham The OP might want to consider getting a nice FPGA board with get started using VHDL or Verilog. I suspect from the OP's comments and replies that this is the probable direction being pointed out. Jon Jon, When you say a "nice FPGA board," what would you suggest? Is there a typical, low cost trainer available? Also, is there a specific VHDL that one would use? Scott >>> > >HI, >>> > > [quoted text clipped - 39 lines] > > Jon >>>> > >HI, >>>> > > [quoted text clipped - 41 lines] >typical, low cost trainer available? Also, is there a specific VHDL that one >would use? Actually, there are a lot of such excellent options, I would leave that up to the OP. But I purchased a small board from Xilinx as my first case, the XESS proto board. It included an XC4010XL. I definitely paid less than $100 for it, but I don't remember the exact amount now. Because I've put more time into using Xilinx parts and didn't run up against problems, that's the way I'd go for another board or my first board, if I did it again. But I am also impressed by BurchED in Australia and I'd have no problem buying their products. I used the software that Xilinx provided. It was just before their web based tools, so I got a full functioning toolkit without any need of web access to use. Not sure what those circumstances would be now. Nor do I know much about what is considered the better VHDL to learn from and about. I would like to hear opinions about that. Speaking of which, I prefer VHDL over verilog. I've learned some of both and at my stage of learning and with my software background, VHDL is a clear winner in terms of readability for me and I'm not aware of there being a downside to it. Jon >> >HI, >> > [quoted text clipped - 29 lines] >I just meant by pre-made that maybe there is a chip that would include >al those NAND and inverters. --- In the example above, you probably already know that an inverter can be made from a NAND by connecting its inputs together, so if you used all NANDs to construct the circuit (which is called a '2 to 1 multiplexer') it would look like this: W>--+------------A | NAND Y--+ X>--|------------B | | | +---A +--A | NAND Y--+ NAND Y--->O +---B | +--B | | +--A | AND Y--+ Y>---------------B There are several chips available which contain four dual-input NAND gates, in both bipolar and CMOS construction and in the 74XX and 4000 families of logic devices. A good site to peruse would be: http://www.ti.com/ and data sheets to download would be: http://focus.ti.com/lit/ds/symlink/sn74ls00.pdf http://focus.ti.com/lit/ds/symlink/cd74hc00.pdf http://focus.ti.com/lit/ds/symlink/cd4011a.pdf As others have mentioned there are also available chips designed as arrays of uncommitted logic gates which can be programmed to yield pretty much any logical function(s) you could want, but I noticed that no one mentioned a Programmable Read Only Memory, in any of its various flavors. Google "PROM" or "EPROM" and also the acronyms earlier presented for some interesting reading. (If you like logic :-)) SignatureJohn Fields Professional Circuit Designer > I noticed that no one mentioned a Programmable Read Only Memory, > in any of its various flavors. It's covered in one of the wikipedia links I posted. Graham >> I noticed that no one mentioned a Programmable Read Only Memory, >> in any of its various flavors. > >It's covered in one of the wikipedia links I posted. --- So what? My point was that no one mentioned it, and no one did. Had they, they would have called it out by name as I did. SignatureJohn Fields Professional Circuit Designer > HI, > [quoted text clipped - 9 lines] > > ken Hi, Ken. There definitely is a digital equivalent. You could do worse than starting with Wikipedia: http://en.wikipedia.org/wiki/Flip-flop_(electronics) http://en.wikipedia.org/wiki/Sequential_logic http://en.wikipedia.org/wiki/State_machine But try to remember that they invented computers to get away from this. Re-inventing the wheel may be helpful to learn how the wheel is made, but after that, just get a wheel. Cheers Chris > HI, > [quoted text clipped - 9 lines] > > ken Hi, Ken. There definitely is a digital equivalent. You could do worse than starting with Wikipedia: http://en.wikipedia.org/wiki/Flip-flop_(electronics) http://en.wikipedia.org/wiki/Sequential_logic http://en.wikipedia.org/wiki/State_machine But try to remember that they invented computers to get away from this. Re-inventing the wheel may be helpful to learn how the wheel is made, but after that, just get a wheel. Cheers Chris |
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