Hardware Rant
This could have gone in general chit-chat, but as it is Spectrum related, and hardware related...
I am in the process of doing some research into converting my 48k Spectrum+ into a 128k machine. The "well known" circuit uses a 20v8 GAL for the logic and now I find out that my programmer can't program GALs :mad:
Bearing in mind that I bought this programmer because it supported a better range of devices, more reliably than the cheap Chinese EBay progammers - which can program GALs.
Ok, I could use an FPGA but that's surface mount (Yuk!) and like using a sledge hammer to crack a nut.
Looks like I'll have to use discrete logic.
Rant over :-o
I am in the process of doing some research into converting my 48k Spectrum+ into a 128k machine. The "well known" circuit uses a 20v8 GAL for the logic and now I find out that my programmer can't program GALs :mad:
Bearing in mind that I bought this programmer because it supported a better range of devices, more reliably than the cheap Chinese EBay progammers - which can program GALs.
Ok, I could use an FPGA but that's surface mount (Yuk!) and like using a sledge hammer to crack a nut.
Looks like I'll have to use discrete logic.
Rant over :-o
Post edited by ramsrc on
Comments
Have a look at the Xilinx XC9536XL and XC9572XL, both available in PLCC.
By the way surface mount isn't that bad, it's a little more time consuming to hand solder compared to pin through hole but it's not hard so long as you have soldering wick and a decent soldering iron. You don't need insanely small soldering iron tips, I use the same tip for through hole and SMD. Also, if you get going with SMD you get access to a whole heap of useful and interesting devices.
I must admit that I hadn't considered a CPLD, I've been away from Hardware for too many years. It looks like I am going to have to move outside of my comfort zone!
You can get breakout boards for all the common package types that break the connections out to pads but this is rather too messy for anything except breadboarding. Really that means a PCB which can be rather daunting however there are a few companies now who will make prototype boards at very reasonable prices.
I had the prototypes for my new flash rom boards made by futurlec.
etc
Oh well, I'll join the party and recommend CPLD's too. Those protoboards Guesser recommend are a time saver for one-offs!
Thanks for all the advice, everybody. I am currently in the process of evaluating my options. I have been putting off attacking surface mount for many years and I have finally reached a point where I cannot really do it any other way.
I jotted down the design in TTL during my lunchbreak and having simplified the Boolean logic I drafted the schematic - only to find I can't easily get the 74LS parts I need anymore. (Or for that matter 74HCT)
Enough! I'm currently installing ISE WebPACK :-o
He made it look easy! My soldering on the other hand would probably best be described as competent - but not expert.
<BEST TERRY THOMAS VOICE>
Fnar Fnar
</TERRY THOMAS>
Hit me up with your address and the GAL code and I will send you a programmed 20v8 =)
In the mean time I am going to experiment a little with CPLDs.
Well, 74HCT is still manufactured and widely available, I've never had a problem getting the ones I need. Certainly Farnell never seems to have a shortage of it.
The CPLD idea appeals to me though. I've been playing with Xilinx's ISE Webpack and have been very impressed.
Is that the UK Farnell, or the German one? You can always say you're a student, after all you're learning :-) (Or ship to your workplace. This is what I do - not because Farnell only sends to companies, but because when the mail comes I'm not at home, so usually I have stuff delivered to work because there will be no one at home to sign for the parcel)
Still, it's somewhat academic - I can get most of what I want from Reichelt, and I usually make do without the rest (or order from RS if really desperate!)
Incidentally, I've just got done doing some fine pitch SMD soldering - by hand - so while it's fresh in my mind some tips on what makes it trouble-free for me:
* Isopropyl alcohol to make sure things are clean first.
* Liberal application of flux. I use a flux pen. Chemtronics No Clean Flux Dispensing Pen (CW8100) - although I still clean it off after soldering because it looks ugly if you don't!
* Kapton tape. Tape the part down to stop it moving. Kapton won't melt when the soldering iron gets close.
* Very fine solder wire. For fine pitch, I've just used 0.23mm wire and it worked really well.
* Solder wick. In case you get bridged pins, it's easy to clean it up with a bit of solder wick.
* Magnifying glass to inspect the pins.
Here's a video of someone doing some *awesome* SMD soldering (in other words, you can't tell it apart from a factory assembled board!) with a pretty normal sloped tip, nothing special or tiny. (The tip I use is a 2mm sloped tip, for soldering 0.5mm pitch devices!)