Problematic PLDs – The Answer is Near…

The problem that I have been having with PLDs in the recent past may be close to being resolved.  The last few times that I’ve ordered GAL22V10s from any source my programmer, a TL866 (aka:  MiniPro), has been unable to program them. Considering that my G80-S Computer requires this PLD for it’s decoding logic, and that many users do not have a means to program these chips, this creates quite a problem.  So I have set out on a quest to see if the problem with the over 120 GAL22V10s that I have have in my possession is truly a problem with the ICs, or if it is an issue with the programmer.  I suspect the second is the cause.

So, I have ordered a batch of boards for the ‘ELM Simple GAL Programmer‘ and have built one to test.  Above is the board.  The person who designed the board used a Male to Male 24-Pin Serial Cable for some reason, rather than a proper Parallel Cable.  I do not know why.  But Since I do not own a 24-Pin Male to Male cable, I’m waiting on one to arrive.  The rest of the board is done.  I’ve already applied voltage and test the VCC and the 15v lines, and adjusted them to their proper voltages.

Assuming this works for programming the 22v10s that I’ve had so many problems with, I will likely redesign this board so that it is a little more proper, and then offer it in the RetroDepot store.  However, I will likely sell off the extra boards that I ordered once I confirm they do in fact work.  Until then, no sense in selling PCBs that I’m unsure of.

N8VEM SBC V2 – Still awaiting shipment

Well, Mouser managed to send an email today letting me know that they have shipped my package which has the needed parts to get this board up and running. However, it looks like the package will not get to me until 1/13/18 (4 more days).  Even though I am only 4:30hrs away from their warehouse.  I’m going to be honest, I’m not very happy with their service this time around.  But I suppose every company is allowed to have a bad day from time to time…

I already have all of the sockets and passive components soldered. I’m just waiting on the chips to stick into the sockets.  As well as an oscillator. I plan on testing this board at 16mhz , but may drop the speed depending on how the initial testing goes.  I decided to go with ACT logic families, since they have a very fast propagation delay, low power consumption, and are CMOS and TTL compatible.


The bare SBC V2 Board


Missing only the chips, the CPU Clock, and a 1k resistor array (RR1).  Well, and it needs a bi-color LED…

I actually had several of the chips needed on hand.  The board currently has a 20mhz CPU (z80 of course), an 8255, an 16C550, and a MAX232CPE.  But I still need to have a few more ICs before this will be able to boot to CP/M.  Still waiting on Mouser…

As you may have noticed in the second picture above, I installed a machine pin DIP-8 socket in place of P4 (CPU Clock).  This allows me to try a variety of oscillators until I find one that works as desired.  The goal is to have a very fast processor, and be able to run the SCG (Sprints and Color Graphics) Card in this computer.  Though I hear that card prefers something in the range of 4mhz.  For some reason I have to believe it can handle more speed.  Maybe the person who suggest this used a slower logic family???

As soon as I have more to report I’ll be back with another post.

Website Update, and Other News…

It’s been a while since I have been able to update the website.  That has mostly been due to the holidays, but also general problems of being an adult, like work…

But, fear not. I have managed to make a few updates this evening.  There is now a downloads section available by using the main menu at the top of the site.  Also, I’ve added tabs for Links, as well as condensed the Store into a tab where the cart and the checkout can be accessed.

I’ve worked on the downloads page to the point that I think it is functional.  It looks ugly to me, but it serves it’s purpose.  Maybe I need some nifty graphics or something…

I’ve got to finish working on the TinyBASIC source.  It has been brought to my attention that there is another issue with it, although it is not something that I have toyed with.  So I’m not sure where it went broken.  The average user will probably not notice it, but if you are trying to use programs found on the web, you may run into problems were it concerns the syntax.

I received a batch of boards for the N8VEM SBC V2, and some Harlequin 48k boards.  I may be offering some of those in the store before long.  I would like to build them first to make sure the boards came out as expected.

I am working on building a N8VEM SBC V2.  I am currently waiting on parts from Mouser.  Their website said that the parts would leave their warehouse 3:30hrs after I ordered 3 days ago, and I received an email this morning stating that they would likely be shipped today. And, they would send me an email when they had shipped.  It’s now 9:30pm and that email has not arrived.  Broken promises….  But I’ll get a blog post, maybe a video, of that up as soon as it’s complete.  I also have an 8-slot ECB backplane on the way from John Coffman.  It’s the 167mm version of that board, so I am really looking forward to getting this setup.  I plan on putting this system into a 19″ 5U rack mount enclosure.  Along with a front panel that displays address, data, and status lights.  I am thinking something along the lines of the Magic-1 as seen here:  http://www.homebrewcpu.com/

I’m also, as we speak, printing up an enclosure for my N8VEM Zeta SBC V2, and the ParPortProp board.  Thats more of a work in progress.  But I may get a few pictures up as soon as it looks halfway decent.  I’m no artist, especially when it concerns 3D objects.  But I try.

So here is to making 2018 a great year!!!