Andrew I was just thinking it might make sense to make small little DIP adaptor boards for the SDRAMs. That way one can switch them around from board to board for debugging etc. They could be very small just slightly larger than the chips themselves but with socket pin holes like we did tor the Cirrus chip only far smaller.
From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of Andrew Lynch
Sent: Sunday, January 06, 2013 6:22 PM
Subject: RE: [N8VEM-S100:1291] LAVA-10 Zener Diode = 1N5226 (3.3v)
To get any sort of useful memory density we’ll need to use the Pseudo-SRAMs at a minimum. Those are only available in TSOP-44 which is SMT but manageable. The alternative is BGA packages which are entirely unmanageable unless you have the IR heat lamp or soldering oven. Both are specialized equipment so the TSOP-44 PSRAMs are a viable if difficult option.
We might be able to use as many as 16 PSRAMs to get to a 16MB board. That seems like the next logical step once we show the 4MB SRAM board is working. Then it is all DRAM based solutions and that is going to get ugly.
I don’t particularly like SMT but recognize there may be no other choices in some instances. Let use them sparingly when needed as needed.
Thanks and have a nice day!
Could use these, in general I like to stick to DIP chips with sockets (and a Zener in this case). Surface mount tend to be a little tricky for some. There is plenty of space on this board. There are DIP “level changers” also, but outfits like Jameco don’t stock them.
As a general question, how do people feel about surface mount chips? I currently working on plans for a 80386 RAM board where capacity is an issue. Do most people fee that could solder SM RAM chips to a board. Really would increase board capacity for pseudo-RAM chips.
John Monahan Ph.D
From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of yoda
Sent: Sunday, January 06, 2013 11:25 AM
Subject: Re: [N8VEM-S100:1282] LAVA-10 Zener Diode = 1N5226 (3.3v)
why not use 74lvxxx logic to interface to the lava board ? - it does the protection and is 5V tolerant - it has been used in propeller interfaces for the same thing and makes the parts count a lot smaller
On Sunday, January 6, 2013 11:51:09 AM UTC-6, lynchaj wrote:
Hi Paul! Thanks! Yes, the 3.3VDC Zener diodes are added after the 100 ohm
resistors for 5V to 3.3V level transition. In theory you don't need them
and adding the Zeners are kind of a "belt and suspenders" approach to level
transition. However the LAVA-10 is one expensive component so it is worth a
the extra expense to protect it. I'd consider them optional but a worthy
investment even if not needed.
Thanks and have a nice day!
> -----Original Message-----
> From: n8ve...@googlegroups.com [mailto:n8vem-
> s1...@googlegroups.com] On Behalf Of Paul Birkel
> Sent: Sunday, January 06, 2013 2:50 AM
> To: n8ve...@googlegroups.com
> Subject: [N8VEM-S100:1271] LAVA-10 Zener Diode = 1N5226 (3.3v)
> Is it intended that 1N5226 (3.3v) Zener diodes be used for the logic-level
> shifting circuits (with the 100 ohm resistors)?