using a 6522 with a 6802

[Lee K. Gleason]

I'm trying to put together a small controller, using a Motorola 6802 (more
or less, a 6800 with some onboard RAM), a 27C512 EPROM, and a 6522 VIA (you
know, old school, circa 1980 style). It's designed in the simplest way
possible, simple chip select, oscillator chip clock, really nothing
complicated about it. I'm having trouble getting it to work though. All the
signals look right, but the 6522 never does anything. I'm wondering if just
connecting the E clock output from the 6802 to the 6522 CLK is causing any
problems, or if more elaborate handling of the timing is necessary. Anyone
out there ever use a 6522 in a 6800 environment successfully? Any tricks to
it?

 

[Tom2000]

I'm trying to put together a small controller, using a Motorola 6802 (more
or less, a 6800 with some onboard RAM), a 27C512 EPROM, and a 6522 VIA (you
know, old school, circa 1980 style). It's designed in the simplest way
possible, simple chip select, oscillator chip clock, really nothing
complicated about it. I'm having trouble getting it to work though. All the
signals look right, but the 6522 never does anything. I'm wondering if just
connecting the E clock output from the 6802 to the 6522 CLK is causing any
problems, or if more elaborate handling of the timing is necessary. Anyone
out there ever use a 6522 in a 6800 environment successfully? Any tricks to
it?

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

 

[Jakthehammer]

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.......

 

[Steve]

I'm trying to put together a small controller, using a Motorola 6802
(more
or less, a 6800 with some onboard RAM), a 27C512 EPROM, and a 6522 VIA
(you
know, old school, circa 1980 style). It's designed in the simplest way
possible, simple chip select, oscillator chip clock, really nothing
complicated about it. I'm having trouble getting it to work though. All
the
signals look right, but the 6522 never does anything. I'm wondering if
just
connecting the E clock output from the 6802 to the 6522 CLK is causing any
problems, or if more elaborate handling of the timing is necessary. Anyone
out there ever use a 6522 in a 6800 environment successfully? Any tricks
to
it?

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

 

[Jim]

I'm trying to put together a small controller, using a Motorola 6802 (more
or less, a 6800 with some onboard RAM), a 27C512 EPROM, and a 6522 VIA (you
know, old school, circa 1980 style). It's designed in the simplest way
possible, simple chip select, oscillator chip clock, really nothing
complicated about it. I'm having trouble getting it to work though. All the
signals look right, but the 6522 never does anything. I'm wondering if just
connecting the E clock output from the 6802 to the 6522 CLK is causing any
problems, or if more elaborate handling of the timing is necessary. Anyone
out there ever use a 6522 in a 6800 environment successfully? Any tricks to
it?

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

 

[Rich Grise]

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

What the hell, build one!
http://freenet-homepage.de/dieter.02/m02.htm
Found on:
http://freenet-homepage.de/dieter.02/
Found on:
http://www.6502.org/homebuilt

Cheers!
Rich

 

[Lee K. Gleason]

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.

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..

 

[Tim Williams]

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

Obviously, just go to the future and purchase a Terminator unit.
http://en.wikipedia.org/wiki/6502#6502_in_popular_culture

Tim

 

[Tom2000]

What the hell, build one!
http://freenet-homepage.de/dieter.02/m02.htm
Found on:
http://freenet-homepage.de/dieter.02/
Found on:
http://www.6502.org/homebuilt

Cheers!
Rich

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

 

[Tom2000]

Obviously, just go to the future and purchase a Terminator unit.
http://en.wikipedia.org/wiki/6502#6502_in_popular_culture

Tim

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

This was my introduction to the 6502:

 

[Tom2000]

Obviously, just go to the future and purchase a Terminator unit.
http://en.wikipedia.org/wiki/6502#6502_in_popular_culture

Tim

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

This was my introduction to the 6502:

http://www.old-computers.com/museum/computer.asp?c=856

This thread is bringing back lots of good memories.

Thanks, Tim!

Tom

 

[Tom2000]

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..

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

 

[Steve]

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..

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

 

[Phil Hobbs]

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

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

Cheers

Phil Hobbs

 

[neon]

you should not mix differnent family and expect it to work even logicaly the are the same