Yup, the ATF22V10 is the one that’s hard to program. I was going to use Lattice parts, but they’re all listed as end of life now. In the long run, I need to learn how to work with CPLDs or FPGAs, but they all seem to need support chips and come in SMD packages.

Yes, the device has output latches when programmed for registered mode.

http://ww1.microchip.com/downloads/en/D ... asheet.pdf

I didn’t bother in this case, since the displays are intended to be always active.

One of those recurring topics for basic single board computers is displaying addresses and data. Using seven segment LED displays seems simple, until you find that converting nybles to 7 segments is not trivial. Hex to 7 segment decoder chips were discontinued years ago and displays with integrated ...

Reviving an old thread, finally back to this after -- a year!? I ultimately dropped the random logic concept, as the parts count explodes when you start adding functionality. Taking a closer look at using the processor to do things, it becomes obvious that you need some form of PLD to hold all the ...

Complete 32.768 kHz can oscillators are easy to come by. Divide the output with a pair of 8 bit counters (74HC590 or equivalent) and you'll get an accurate 60 Hz square wave. It's good enough for clocks...

Still here, still working on the front panel concept. Life of course has intervened, with the early sale of my house and delays for my new house causing all my hardware and tools to be in storage! So, this is a paper exercise for now. I do have a bit to show, the attached photo is a partial design ...

Done traveling for the holidays, and still thinking about the front panel design. Here's a block diagram of how I think it will go at this point. I want to keep the clock local on the processor board, so the front panel will inhibit the processor clock and generate its own clock pulses for its ...

So, I've done some sketching using the reset/BE and external counter concept, and it really doesn't do what I want. For boot loading it's clearly the superior solution, but I'm more interested in controlling the µP and being able to single step through small programs. Deadstart loading is necessary ...

So, the more I dig into the processor as counter concept, the more complex it becomes. It can't really be made modular, because you have to split the data bus with a bidirectional transceiver and gate it correctly. You have to count cycles from the last sync so you can gate the correct things to the ...

Hmm. Rather than counting, isn't what we really want to do (for the 16-switch concept) sequencing? Why not just clock a bit across a shift register to do the chip selects in turn? Then preset the shift register on SYNC.

A simpler way than what you described about the Altair is:

While simpler, I think having the ability to set the PC register is handy, and then you don't have to worry about managing address lines - once you add a separate address counter, what you see on the lines is a bit removed from the ...

Especially since the added hardware is so trivial, I would encourage you to go ahead and allow for them. Interrupts are super valuable and a great strength of the '02. At least run the IRQ\ output of the VIA over to the IRQ\ input of the '02.

Ok, I can see that - as you say, the addition is ...

Hello folks, new member and first post here. This might go better in Newbies, but I'm going to focus on hardware, so here we are...

I got into computers when my dad built a COSMAC Elf II kit, and began I programming in 1802 machine language on graph paper. He and I soon moved on the the 6502, and ...