https://repository.rice.edu/bitstreams/1e0edebf-f0de-4f73-8092-cd8038912e11/download
pages 17-18
2.6.6 A Special Characteristic of the R6522
The R6S22 Versatile Interface Adapter was actually originally designed
to be used with the 6500 family of microprocessors. One of the major characteristics of the 6500 family is that the control and address
busses are always driven. They are never allowed to float.
During testing of the prototype microprocessor board the R6522s were
found to exhibit strange behavior. The parallel output lines would
change states randomly when the processor executed the STOP instruction, which floats the address, data and control lines. At first the problem
was unclear, as some chips exhibited this phenomena, and others worked correctly. The outputs would sometimes change several seconds after the
STOP instruction had been executed. This behavior was very mysterious,
since the devices changed their outputs despite the fact that their chip selects were negated. After much experimenting it was discovered that in certain circumstances it was possible to change the outputs by shorting
the floating address lines to ground.
At this point die manufacturer was contacted, and an application
engineer explained politely that this was an undocumented feature of the
part However, Rockwell had sold the R6S22 to Apple for use in the
Macintosh, and during that transaction a Rockwell engineer discovered
that pull-up resistors on the address bus fixed the problem. Rockwell
also decided to fix the part The new part is called the R65NC22. The microprocessor board has pull-ups allowing original R6S22 parts to be
used, although all the systems built contain the new part
Sounds Image Adapter/A like. "high-speed video interface"
Louis Ohland wrote:
https://repository.rice.edu/bitstreams/1e0edebf-f0de-4f73-8092-cd8038912e11/download
pages 17-18
2.6.6 A Special Characteristic of the R6522
The R6S22 Versatile Interface Adapter was actually originally designed
to be used with the 6500 family of microprocessors. One of the major
characteristics of the 6500 family is that the control and address
busses are always driven. They are never allowed to float.
During testing of the prototype microprocessor board the R6522s were
found to exhibit strange behavior. The parallel output lines would
change states randomly when the processor executed the STOP
instruction, which floats the address, data and control lines. At
first the problem was unclear, as some chips exhibited this phenomena,
and others worked correctly. The outputs would sometimes change
several seconds after the STOP instruction had been executed. This
behavior was very mysterious, since the devices changed their outputs
despite the fact that their chip selects were negated. After much
experimenting it was discovered that in certain circumstances it was
possible to change the outputs by shorting the floating address lines
to ground.
At this point die manufacturer was contacted, and an application
engineer explained politely that this was an undocumented feature of
the part However, Rockwell had sold the R6S22 to Apple for use in the
Macintosh, and during that transaction a Rockwell engineer discovered
that pull-up resistors on the address bus fixed the problem. Rockwell
also decided to fix the part The new part is called the R65NC22. The
microprocessor board has pull-ups allowing original R6S22 parts to be
used, although all the systems built contain the new part
Ooohh..
Louis Ohland wrote:
Sounds Image Adapter/A like. "high-speed video interface"
Louis Ohland wrote:
https://repository.rice.edu/bitstreams/1e0edebf-f0de-4f73-8092-cd8038912e11/download
pages 17-18
2.6.6 A Special Characteristic of the R6522
The R6S22 Versatile Interface Adapter was actually originally
designed to be used with the 6500 family of microprocessors. One of
the major characteristics of the 6500 family is that the control and
address busses are always driven. They are never allowed to float.
During testing of the prototype microprocessor board the R6522s were
found to exhibit strange behavior. The parallel output lines would
change states randomly when the processor executed the STOP
instruction, which floats the address, data and control lines. At
first the problem was unclear, as some chips exhibited this
phenomena, and others worked correctly. The outputs would sometimes
change several seconds after the STOP instruction had been executed.
This behavior was very mysterious, since the devices changed their
outputs despite the fact that their chip selects were negated. After
much experimenting it was discovered that in certain circumstances it
was possible to change the outputs by shorting the floating address
lines to ground.
At this point die manufacturer was contacted, and an application
engineer explained politely that this was an undocumented feature of
the part However, Rockwell had sold the R6S22 to Apple for use in the
Macintosh, and during that transaction a Rockwell engineer discovered
that pull-up resistors on the address bus fixed the problem. Rockwell
also decided to fix the part The new part is called the R65NC22. The
microprocessor board has pull-ups allowing original R6S22 parts to be
used, although all the systems built contain the new part
A dual-port FIFO memory with unlimited expansion capability
Published in: Electronics and Power ( Volume: 31, Issue: 11.12, November-December 1985)
Louis Ohland wrote:
Ooohh..
Louis Ohland wrote:
Sounds Image Adapter/A like. "high-speed video interface"
Louis Ohland wrote:
https://repository.rice.edu/bitstreams/1e0edebf-f0de-4f73-8092-cd8038912e11/download
pages 17-18
2.6.6 A Special Characteristic of the R6522
The R6S22 Versatile Interface Adapter was actually originally
designed to be used with the 6500 family of microprocessors. One of
the major characteristics of the 6500 family is that the control and
address busses are always driven. They are never allowed to float.
During testing of the prototype microprocessor board the R6522s were
found to exhibit strange behavior. The parallel output lines would
change states randomly when the processor executed the STOP
instruction, which floats the address, data and control lines. At
first the problem was unclear, as some chips exhibited this
phenomena, and others worked correctly. The outputs would sometimes
change several seconds after the STOP instruction had been executed.
This behavior was very mysterious, since the devices changed their
outputs despite the fact that their chip selects were negated. After
much experimenting it was discovered that in certain circumstances
it was possible to change the outputs by shorting the floating
address lines to ground.
At this point die manufacturer was contacted, and an application
engineer explained politely that this was an undocumented feature of
the part However, Rockwell had sold the R6S22 to Apple for use in
the Macintosh, and during that transaction a Rockwell engineer
discovered that pull-up resistors on the address bus fixed the
problem. Rockwell also decided to fix the part The new part is
called the R65NC22. The microprocessor board has pull-ups allowing
original R6S22 parts to be used, although all the systems built
contain the new part
The main application of the MK4501 is as a rate buffer, sourcing and absorbing data at different rates, (e.g., interfacing fast
processors and slow peripherals).
Louis Ohland wrote:
A dual-port FIFO memory with unlimited expansion capability
Published in: Electronics and Power ( Volume: 31, Issue: 11.12,
November-December 1985)
Louis Ohland wrote:
Ooohh..
Louis Ohland wrote:
Sounds Image Adapter/A like. "high-speed video interface"
Louis Ohland wrote:
https://repository.rice.edu/bitstreams/1e0edebf-f0de-4f73-8092-cd8038912e11/download
pages 17-18
2.6.6 A Special Characteristic of the R6522
The R6S22 Versatile Interface Adapter was actually originally
designed to be used with the 6500 family of microprocessors. One of
the major characteristics of the 6500 family is that the control
and address busses are always driven. They are never allowed to float. >>>>>
During testing of the prototype microprocessor board the R6522s
were found to exhibit strange behavior. The parallel output lines
would change states randomly when the processor executed the STOP
instruction, which floats the address, data and control lines. At
first the problem was unclear, as some chips exhibited this
phenomena, and others worked correctly. The outputs would sometimes
change several seconds after the STOP instruction had been
executed. This behavior was very mysterious, since the devices
changed their outputs despite the fact that their chip selects were
negated. After much experimenting it was discovered that in certain
circumstances it was possible to change the outputs by shorting the
floating address lines to ground.
At this point die manufacturer was contacted, and an application
engineer explained politely that this was an undocumented feature
of the part However, Rockwell had sold the R6S22 to Apple for use
in the Macintosh, and during that transaction a Rockwell engineer
discovered that pull-up resistors on the address bus fixed the
problem. Rockwell also decided to fix the part The new part is
called the R65NC22. The microprocessor board has pull-ups allowing
original R6S22 parts to be used, although all the systems built
contain the new part
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