using a 6522 with a 6802

Wow, last I checked 6522s only worked at 1 or 2 MHz. What frequency is the E clock running at? The 6522 is a great chip AFAIR.

Wow, a blast from the past.

I've done it, but that was over 20 years ago, and certainly don't remember exactly how. Hanigng a 6522 on the Motorola bus isn't difficult, though. I'd suggest that you carefully read the data sheets for both chips, paying particular attention to the clock phase, R/W, and chip select conditions. You'll find your solution there.

If you still have trouble, switch to a 6502 processor. If you can find one. :-)

Good luck!

Tom

Time to use ICE....Heehee.......

I've used that combination successfully. The 6522 was a much better UART than the Motorola part was. But unfortunately, it was so long ago that I can't remember how the clocking was done. I doubt it was much external logic - we didn't use much more than PAL's in those days. Check to see if its clock needs to be inverted relative to the 6802 to align the Rd/Wr or CS edges where they need to be. I think clock phase was one of the differences between the 6502 and 6802 processors.

I'm curious as to why you would not just use one of the thousands of available Flash based microcontrollers for your project. They cost less, there are less obsolescence issues, and all the hardware is already debugged for you. Most have serial emulation available for under $100. I loved the

6809 in its day, but its just been overshadowed in speed, size and cost. If your software is expected to have any complexity at all, don't underestimate the difficulties of debugging without emulation. It takes 10 times longer than it will with even the simplest emulation tools.

Good luck with your project, Steve

I just looked at some old notes that I had - using a 68HC11 and a 6522. It looks like I ran the E line directly into ph2 (pin 25) - no special buffering at all. I put A12 into CS1 and then used a 74hc139 to decode A13-A14-A15 into CS2. Note that CS2 is inverted so is active low. IRQ, and R/W run straight in. If you're careful with your connections, it should work (I know that board is still around here somewhere - it worked well for many years for me).

Jim

What the hell, build one!

Found on: Found on:

Cheers! Rich

debugged

If

underestimate

Thanks all for the info. I'm doing this out of nostalgia - when 6800s were new, I was too busy and too hardware-ignorant to experiment with them. Now, I've got some spare time, and a lot more expereince under my belt, so I'm revisiting the chips I missed out on back then..

-- Lee K. Gleason N5ZMR Control-G Consultants snipped-for-privacy@comcast.net

Obviously, just go to the future and purchase a Terminator unit.

Tim

-- Deep Fryer: A very philosophical monk. Website @

Good grief! I can understand an attachment to a particular processor or family, (Like a previous poster, I was also pretty fond of the

6809), but this is going to extremes.

Thanks, Rich!

Tom

Wow. Is there *anything* that isn't in the Wikipedia?

This was my introduction to the 6502:

Wow. Is there *anything* that isn't in the Wikipedia?

This was my introduction to the 6502:

This thread is bringing back lots of good memories.

Thanks, Tim!

Tom

Well, Lee, if it's about nostalgia, then all is forgiven. :-) I can certainly understand your motivation, and it's a good one. (I just received an HP-11C calculator that I purchased on eBay for nothing more than nostalgia.)

FWIW, I used a 6802 for the first computer that I "designed" and built from scratch.

I wire wrapped it, and wrote my own monitor by hand-assembling the code, then punching it into a borrowed EPROM programmer by hand. It took quite a few tries since debugging involved punching another EPROM.

I had a lot of fun with that project, and really learned a bunch.

Enjoy your project. I know you're having fun.

Very 73,

Tom AB9B

Nothing wrong with having fun....

Compared with Intel micros, the Motorola parts were wonderful for assembly language: regular architectures, CC flags that were consistent regardless of the op code, and few special purpose registers. When the 6809 came out, it fixed the biggest 6802 flaw IMO - a single index register with limited addressing modes.

I'm surprised you can still buy the parts.

Good luck Steve

Sure--such as any balanced and detailed discussion of controversial issues.

Cheers

Phil Hobbs