The Southwest Technical Products MP-N Calculator Interface interfaces the SWTPC 6800 Computer System thru a Peripheral Interface Adapter (PIA) to the National Semiconductor MM57109 Number Oriented Processor. This "processor" is a Reverse Polish Notation (RPN) calculator chip without the internal keypad interfacing circuitry which has made interfacing to calculator chips so difficult in the past. This chip allows data and instruction entry in conventional binary form and speeds entry with the elimination of the debounce circuitry built into conventional calculator chips. It is called a processor because it has instructions and control lines which allow it to operate in conjunction with ROM and RAM as a stand alone numerical processor. It may however be operated as a computer peripheral for numerical calculation and this is the configuration in which the chip has been implemented.
Introduced by Southwest Technical Products Corporation in 1977. The MP-N kit cost $45
Board Photo (50K JPG)
Board Photo High Resolution (146K JPG)
Assembly Instructions (222K PDF)
ASCII to HEX Chart (7K PDF)
RPN Introduction (223K PDF)
CALC1 Program Source (5K TXT)
CALC1 Program S1 Load (2K TXT)
I would like to thank Todd Silk for sending me a scanned version of the MP-N documents and Joe Lang for lending me an original printed copy.
Michael Holley's SWTPC Collection Home Page