Post by thread:[PIC]: Driving 74ALS244 from PIC Clock

This is a pretty good source (Philips) of TTL data sheets if you want to find out the input/output/speed/power specs of the various logic families http://www.semiconductors.com/handbook/handbook_45.html There is also this recent post of a document called "Motorola Logic Families, Which is best for you ?" http://design.stanford.edu/spdl/logic/which_is_best.html -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Thanks for helping me reach a better solution. I have some MC4024 clock chips that are now about 25 years old, but they may solve the problem. They contain an oscillator block that will accept either a capacitor between two designated pins or a parallel crystal in the same spot. Their outputs are TTL and they are pretty rugged. I know the output of one of these won't even notice the 16C64's clock input if it is configured as a LP and there will be more than enough drive left over for the equally ancient 7493 counter that will divide that clock down for another part of the system that needs it. I wonder if I am the only one who doesn't have the heart to throw out chips that still work? A couple of these MC4024's have been in probably 5 or 6 projects that lived out their useful lives over the past couple of decades, but I just pull them out of the socket and put them in to something else as long as they still work. Martin McCormick WB5AGZ Stillwater, OK OSU Center for Computing and Information Services Data Communications Group Dan Michaels writes: {Quote hidden}>Martin McCormick wrote: >Martin, > >There have been so many threads on piclist about people having >problems with the PIC oscillators that your project sounds like >a try-it-and-see experiment. I have run an MC145436 DTMF chip >directly off the OSCOUT pin with no problems - 3.57 Mhz xtal >and XT oscillator. > >It may also depend upon whether you have a '64, '64A, or '64B >[or equiv in '7x series], as people seem to be having more >problems with the newer chips. > >Also, you may need to select a more powerful oscillator option >than you might otherwise be using, ie, HS rather than XT, etc. >=============== > >> I need to divide that frequency down to 1.024 megahertz >>and, if the 74ALS244 can buffer that clock, I can then drive an >>old 7493 4-bit counter to get the clock I want for a particular >>part of the circuit that needs it. >> > >Suggest you *not* try driving a 74LS or 73xx part. 74ALS ???? >Better to try a 74HC - cheap and available from Radio Shack this >afternoon. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Martin McCormick wrote: ......... > I wonder if I am the only one who doesn't have the heart >to throw out chips that still work? A couple of these MC4024's ........ I take those old chips and stick them in my tires in the wintertime. They make really good tire studs. Seriously - try 74HC chips, minimal loading and cheap. - DanM -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Martin McCormick wrote: > Thanks for helping me reach a better solution. I have > some MC4024 clock chips that are now about 25 years old, but they > may solve the problem. They contain an oscillator block that > will accept either a capacitor between two designated pins or a > parallel crystal in the same spot. Their outputs are TTL and > they are pretty rugged. I know the output of one of these won't > even notice the 16C64's clock input if it is configured as a LP > and there will be more than enough drive left over for the > equally ancient 7493 counter that will divide that clock down for > another part of the system that needs it. > > I wonder if I am the only one who doesn't have the heart > to throw out chips that still work? A couple of these MC4024's > have been in probably 5 or 6 projects that lived out their useful > lives over the past couple of decades, but I just pull them out > of the socket and put them in to something else as long as they > still work. Throw them out??? I still horde them in my inventory! 35 MC4024 Dual Voltage Controlled Multivibrator 45 MC4324 Dual Voltage Controlled Multivibrator > > > Martin McCormick WB5AGZ Stillwater, OK > OSU Center for Computing and Information Services Data Communications Group > -- * | __O Thomas C. Sefranek spam_OUTtcsTakeThisOuTcmcorp.com |_-\<,_ Amateur Radio Operator: WA1RHP (*)/ (*) Bicycle mobile on 145.41, 448.625 MHz ARRL Instructor, Technical Specialist, VE Contact. hamradio.cmcorp.com/inventory/Inventory.html http://www.harvardrepeater.org -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.