cormack@crg5.UUCP (Mike Cormack) (02/07/90)
aez@Data-IO.COM (Adam Zilinskas) writes: >Reasons for using PALs: >1. Inventory. Many of the larger PIC (Programmable IC) chips can emulate > any TTL functions that you could use in a design. Its your choice to Think real estate here too. 1 PAL uses much less space than several glue logic devices. This can be a crucial in a board design. A reduced parts count is always a nice idea and PALs can help out immensely. >2. Board changes (only matters when making PCB, only slightly matters > if doing wirewrap). A new PIC and be programmed and patch a circuit > within hours/minutes compared to cutting traces on boards and patch I know this one personally. Reworking a board stinks and the reliability decreases quickly once wires are added. In some cases you can't add wires. A primary DFM rule is no wires at FCS and a board turn if > 4 mod wires need to be added. It's a competitive world out there and reliability is very important. Pals can be much easier to use for design changes and sometimes are the only choice. >Reasons for not using PALs: >1. You have to program them. For productions lines of making thousa >2. You have to program them. Most of the programming languages for >3. You have to program them. A hobbyist can go to Radio Crack and get glue O.K. we get your point but I think that your not giving H.W. guys enough credit (you sound kinda biased ;-). Gang programmers are great looking but they're kinda spendy. Another thing you don't point out is that when a person has to program a PAL that means they have to touch it. That's a handling issue which can cause all kinds of problem for assembly folks. The first is ESD and right behind is orientation problems. At least with glue logic you can have a machine stuff them in your PCB and a person doesn't have to touch it. (That's providing you have an auto-inserter:-) >I have tried to keep out any overt advertisements about what Data I/O provides You've given some good advice and a little advert is o.k. It's good stuff so some advert is fine. Some other things. If your volume is large enough, you could get a PAL vendor to burn the fuses as they make it. They use laser etching for that. You can solder PALs into your PCB once your confident that there are no bugs. (That may take some time). Pals can be reliable (less than a 100 PPM). mike per yr you could probably have a pal vendor progra
elliott@optilink.UUCP (Paul Elliott x225) (02/09/90)
In article <19023@crg5.UUCP>, cormack@crg5.UUCP (Mike Cormack) writes: > [...] > Think real estate here too. 1 PAL uses much less space than several > glue logic devices. This can be a crucial in a board design. A reduced > parts count is always a nice idea and PALs can help out immensely. > [...] One thing that bugs me about this is that I can't seem to find any of the 20-pin PALs in surface-mount packages (CMOS would be especially usefull). In the days of DIPs, squeezing 3 or 5 16-pin DIPs into one 20-pin PAL made good sense, at least from a space standpoint. Now, I find it hard to justify using a 20-pin DIP PAL when I can fit the same logic in about the same space using SMT (SMT = Surface Mount Technology) HCMOS. On a SMT board we want to avoid through-hole DIPs where possible as additional manufacturing steps are required, so the PAL has two strikes against it. Yes, I am aware of the larger PALS in the 28 PLCC (and up) packages, and we do use them where applicable, but for smaller glue-logic jobs the SMT logic chips have become more attractive again. Another reason that random-logic chips remain a choice is the proliferation of simulation tools in the workplace. When PALs hit the world, often a PAL design could be simulated much more easily than the equivalent discrete logic design. More than once, I designed a function with a PAL just to check out the logic, then implemented it with the equivalent logic chips, because my power budget demanded it. The die sizes in the erasable PALS (as viewed through the window) look pretty big; is this the limiting factor in package size? If anyone out there knows of an EP310-equivalent functionality part in a SMT package, let me know. Even a low-power CMOS 16L8/16R8 would be nice. -- Paul M. Elliott Optilink Corporation (707) 795-9444 {pyramid,pixar,tekbspa}!optilink!elliott "The dog ate my disclaimer."
phil@pepsi.amd.com (Phil Ngai) (02/10/90)
In article <3120@optilink.UUCP> elliott@optilink.UUCP (Paul Elliott x225) writes: |One thing that bugs me about this is that I can't seem to find any of the |20-pin PALs in surface-mount packages (CMOS would be especially usefull). I can assure you that 20-pin PALs in surface-mount packages are available. Try talking to the bigger PAL makers. CMOS is also available, as are quarter power high speed (15 ns) PALs which are electrically erasable. (since they are EE, you don't have to pay for a window, it comes in a regular low cost plastic package) -- Phil Ngai, phil@amd.com {uunet,decwrl,ucbvax}!amdcad!phil When guns are outlawed, only governments will have guns.