7 Jun
2002
7 Jun
'02
11:33 a.m.
From: "Ben Franchuk"
<bfranchuk(a)jetnet.ab.ca>
Loboyko Steve wrote:
Hi
Instructions that would continuously increment the address
are vary useful for debugging address decoding problems.
On an 8080, about the only useful sequence is to have
a pop and jmp, using 4 locations.
It may have been that the 6800 one was a debug instruction
that was designed in.
Dwight
I'm building a 6800 machine right now and I was
wondering about this "Halt and Catch on Fire"
instruction. Is this for real. This is a serious
question. Is there actually an instruction that will
overheat the chip?
Not on the 6800 but I believe some FORTH chips have that problem.
This instruction for the 6800 if remember right just continually
increments the address bus, ignoring any data read. Only a hard
RESET will reset the machine from this state. I think the opcode
is $00.
7 Jun
7 Jun
11:55 a.m.
I worked with a 6809 system back in the early 80s which
had an LED board to display the state of all of the system
signals. I don't recall the OP code, but there was one
which would continuously cycle the address, data, and
other signals until reset. It made the LEDs light up
like a christmas tree.
--tom
At 09:33 AM 6/7/02 -0700, you wrote:
From: "Ben
Franchuk" <bfranchuk(a)jetnet.ab.ca>
Loboyko Steve wrote:
Hi
Instructions that would continuously increment the address
are vary useful for debugging address decoding problems.
On an 8080, about the only useful sequence is to have
a pop and jmp, using 4 locations.
It may have been that the 6800 one was a debug instruction
that was designed in.
Dwight
I'm building a 6800 machine right now and I was
wondering about this "Halt and Catch on Fire"
instruction. Is this for real. This is a serious
question. Is there actually an instruction that will
overheat the chip?
Not on the 6800 but I believe some FORTH chips have that problem.
This instruction for the 6800 if remember right just continually
increments the address bus, ignoring any data read. Only a hard
RESET will reset the machine from this state. I think the opcode
is $00.
1:15 p.m.
I have been told, but never tried myself that the 6809 acts as a 16-bit
counter on the address lines when it finds two data bits shorted
together.
The 68000 was said by the same guy to "pull the pins out of the socket",
i.e., make all outputs high-Z.
Tom Uban wrote:
I worked with a 6809 system back in the early 80s which
had an LED board to display the state of all of the system
signals. I don't recall the OP code, but there was one
which would continuously cycle the address, data, and
other signals until reset. It made the LEDs light up
like a christmas tree.
--
Andreas Freiherr
Vishay Semiconductor GmbH, Heilbronn, Germany
http://www.vishay.com
1:20 p.m.
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