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6802 clock

L

Lee K. Gleason

Jan 1, 1970
0
I'm building a simple 6802 single board system. I want to drive the CPU
with an external oscillator, rather than using a crystal (got lots of 4 pin
oscillators, not so many crystals). When using a crystal, the frequency of
the crystal gets divided down by 4 by an internal part of the processor (so
you use a 4 MHz crystal for a 1MHz clock).

When using an external oscillator, like I want to do, does the same divide
by 4 occur? That is, should I use a 4 MHz external oscillator, or a 1 MHz
oscillator for a 1 MHz system clock?

Lee K. Gleason N5ZMR
Control-G Consultants
[email protected]
 
J

John Fields

Jan 1, 1970
0
I'm building a simple 6802 single board system. I want to drive the CPU
with an external oscillator, rather than using a crystal (got lots of 4 pin
oscillators, not so many crystals). When using a crystal, the frequency of
the crystal gets divided down by 4 by an internal part of the processor (so
you use a 4 MHz crystal for a 1MHz clock).

When using an external oscillator, like I want to do, does the same divide
by 4 occur? That is, should I use a 4 MHz external oscillator, or a 1 MHz
oscillator for a 1 MHz system clock?
 
B

Bozzion

Jan 1, 1970
0
Lee K. Gleason said:
I'm building a simple 6802 single board system. I want to drive the CPU
with an external oscillator, rather than using a crystal (got lots of 4 pin
oscillators, not so many crystals). When using a crystal, the frequency of
the crystal gets divided down by 4 by an internal part of the processor (so
you use a 4 MHz crystal for a 1MHz clock).

When using an external oscillator, like I want to do, does the same divide
by 4 occur? That is, should I use a 4 MHz external oscillator, or a 1 MHz
oscillator for a 1 MHz system clock?

Lee K. Gleason N5ZMR
Control-G Consultants
[email protected]

why not? isn't the devider on chip?
 
F

Frank

Jan 1, 1970
0
By the way who makes the 6802, is Motorola still around?

I'm building a simple 6802 single board system. I want to drive the CPU
with an external oscillator, rather than using a crystal (got lots of 4 pin
oscillators, not so many crystals). When using a crystal, the frequency of
the crystal gets divided down by 4 by an internal part of the processor (so
you use a 4 MHz crystal for a 1MHz clock).

When using an external oscillator, like I want to do, does the same divide
by 4 occur? That is, should I use a 4 MHz external oscillator, or a 1 MHz
oscillator for a 1 MHz system clock?

Lee K. Gleason N5ZMR
Control-G Consultants
[email protected]
 
J

John Fields

Jan 1, 1970
0
By the way who makes the 6802, is Motorola still around?

---
Motorola spun off their µC product line to Freescale Semiconductor,
but I don't think you're going to find much 6802 around, since it's
been obsolete for a while.

Freescale suggests Rochester Electronics as a possible source, and
Google will give you lots of hits. If what you're doing is new, why
do you want to use a 6802 anyway?

If you choose to reply, it's considered, in this group, to be
courteous if you bottom post.
 
F

Frank

Jan 1, 1970
0
No I was just asking?
Motorola came up with a good range of micro, I went to a few of there
seminars, back in the 70's


By the way who makes the 6802, is Motorola still around?

---
Motorola spun off their µC product line to Freescale Semiconductor,
but I don't think you're going to find much 6802 around, since it's
been obsolete for a while.

Freescale suggests Rochester Electronics as a possible source, and
Google will give you lots of hits. If what you're doing is new, why
do you want to use a 6802 anyway?

If you choose to reply, it's considered, in this group, to be
courteous if you bottom post.
 
K

Karl Uppiano

Jan 1, 1970
0
Frank said:
No I was just asking?
Motorola came up with a good range of micro, I went to a few of there
seminars, back in the 70's




---
Motorola spun off their µC product line to Freescale Semiconductor,
but I don't think you're going to find much 6802 around, since it's
been obsolete for a while.

Freescale suggests Rochester Electronics as a possible source, and
Google will give you lots of hits. If what you're doing is new, why
do you want to use a 6802 anyway?

Sometimes a good 8-bit 1 MHz processor is all you need.
 
J

John Fields

Jan 1, 1970
0
Sometimes a good 8-bit 1 MHz processor is all you need.

---
Yes, but that's not the point, which is that the 6802 is obsolete and
only available from "surplus" dealers.

For a desperate one-off, that might be OK, but going through the
expense and hassle of stepping back in time when _many_ good 8 bit µC
are available for cheap in the present hardly makes the exercise seem
worth while.
 
R

Rich Grise

Jan 1, 1970
0
Yes, but that's not the point, which is that the 6802 is obsolete and only
available from "surplus" dealers.

For a desperate one-off, that might be OK, but going through the expense
and hassle of stepping back in time when _many_ good 8 bit µC are
available for cheap in the present hardly makes the exercise seem worth
while.

John is absolutely right. For the effort it would take to track down
data sheets and crap on that old of a part simply doesn't make any
sense. I did a quick google on "6802 data sheet", without the quotes,
and out of thousands of answers, none of them was about the old Moto
micro. Heck, I saw a Basic Stamp Development Kit in Fry's not too
long ago, for about a hundred and twenty-five bucks.

What country are you in?

Good Luck!
Rich
 
J

James Sweet

Jan 1, 1970
0
---
Yes, but that's not the point, which is that the 6802 is obsolete and
only available from "surplus" dealers.

For a desperate one-off, that might be OK, but going through the
expense and hassle of stepping back in time when _many_ good 8 bit µC
are available for cheap in the present hardly makes the exercise seem
worth while.


Quite a few people build things using obsolete microcontrollers just because
they can, I agree that if this is a production device then there's better
choices, but if just fooling around or making something nostalgic then go
for it.
 
K

Karl Uppiano

Jan 1, 1970
0
John Fields said:
---
Yes, but that's not the point, which is that the 6802 is obsolete and
only available from "surplus" dealers.

For a desperate one-off, that might be OK, but going through the
expense and hassle of stepping back in time when _many_ good 8 bit µC
are available for cheap in the present hardly makes the exercise seem
worth while.

I have brand new stuff in my junk box that has been obsolete for decades. If
I have it, I'll use it, if only out of a sense of frugality. If I were
building a commercial product, then availability would definitely be a
primary consideration.
 
J

Jim Adney

Jan 1, 1970
0
If you choose to reply, it's considered, in this group, to be
courteous if you bottom post.

Gee, John, just being difficult, or trying to start a war?

-
 
J

james

Jan 1, 1970
0
A 6802 is essentially a MC6800, MC6875 and a MC6810 integrated into
one IC. The MC6802 intruction set is the same as the MC6800.

The MC6801/3 has increased instructions.

IF you really want a kicked up 6800, try opencores.org. There is a
6800 core that will drop into a Spartan 2 FPGA and runs at a E clock
frequency of 12.5 MHz.

Today there are a few of the older 8 bit micros that have FPGA open
source cores that can run at higher speeds than the originals. There
is even a Z80 core that runs at 35Mhz.

james
 
T

Tam/WB2TT

Jan 1, 1970
0
Lee K. Gleason said:
I'm building a simple 6802 single board system. I want to drive the CPU
with an external oscillator, rather than using a crystal (got lots of 4
pin
oscillators, not so many crystals). When using a crystal, the frequency of
the crystal gets divided down by 4 by an internal part of the processor
(so
you use a 4 MHz crystal for a 1MHz clock).

When using an external oscillator, like I want to do, does the same
divide
by 4 occur? That is, should I use a 4 MHz external oscillator, or a 1 MHz
oscillator for a 1 MHz system clock?

Lee K. Gleason N5ZMR
Control-G Consultants
[email protected]
You might want to check out one of the 6805 variants. They may still be in
production. BTW, if you want to do it on the cheap, use a ~3.58MHz color
burst crystal.

Tam
 
L

Lee K. Gleason

Jan 1, 1970
0
"> >>> Freescale suggests Rochester Electronics as a possible source, and
John is absolutely right. For the effort it would take to track down
data sheets and crap on that old of a part simply doesn't make any
sense. I did a quick google on "6802 data sheet", without the quotes,
and out of thousands of answers, none of them was about the old Moto
micro. Heck, I saw a Basic Stamp Development Kit in Fry's not too
long ago, for about a hundred and twenty-five bucks.

What country are you in?

Good Luck!
Rich

It's just for fun - I've got a few of them, and I always wanted to make a
small system out of a 6800 family processor, ever since they were new. The
6802 means I can use the on board memory for the stack and not have any
RAM - makes the minimalist retro system one chip smaller...when I get this
one going, I'm gonna do a Z80 and maybe a TI 9900 - I've got plenty of chips
from that era due to diligent scavenging, and now I've got a little free
time to experiment...it's just for, you know...kicks...

Thanks all for the answer - I'm soldering in a 4 MHz can oscillator
tonight...the LEDs will be blinking soon...

Lee K. Gleason N5ZMR
Control-G Consultants
[email protected]
 
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