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Canon Canola L121

Date of introduction:  1971 Display technology:  Nixie
New price:   Display size:  12
Size:  9.7" x 9.1" x 2.6"     
Weight:  4 pounds 9 ounces Serial No:  411309
Batteries:  n.a. Date of manufacture:  year 1971
AC-Adapter:  220V Origin of manufacture:  Japan
Precision:  12  Integrated circuits:  TMC1733, TMC1753, TMC1754, TMC1807
Memories:  1    
Program steps:   Courtesy of:  Joerg Woerner

The Canon Canola L121 represents the first desktop calculator using Large-Scale-Integrated (LSI) circuits and was available in 1971. 

L121_IC.jpg (145492 Byte)From the technical view the L121 is from great interest, it uses the TMC1733, TMC1753, TMC1754, TMC1755 (or TMC1807) calculator chip set developed by Texas Instruments. The chip numbers imply that the L121 followed immediately the famous Pocketronic with the three TMC1730, TMC1731, TMC1732 LSI circuits. 

Each of the four chips provide a specific functional part of the logic of the machine.

Data Chip (TMC1733) contains the majority of the working registers of the machine, logic for routing and some processing of data as it is routed between the various registers, and some Nixie display decoding/multiplexing logic. TMC1733A.jpg (70235 Byte)
Timing Chip (TMC1753) provides for controlling and coordinating the operations of the calculator, as well as providing for some miscellaneous functions such as keeping track of decimal point location. TMC1753A.jpg (63851 Byte)
Entry Chip (TMC1754) provides the logic for handling the input from the keyboard. It takes care of key debouncing, locking the keyboard when errors exist, keyboard encoding, and other input-related functions. TMC1754A.jpg (60688 Byte)
Arithmetic Chip (TMC1807, apparently an updated version of the TMC1755 mentioned in the service manual for the machine) contains the logic that actually performs arithmetic operations. TMC1807.jpg (68963 Byte)
The already mentioned Pocketronic used an unique thermal printer to display the calculating results. Why ? 
The LED Display (Light-Emitting-Diode) wasn't yet developed and the already developed Nixie tubes huge and running on high voltages.
L121_Nixie0.jpg (28463 Byte)
One of the 12 Nixie tubes in action. Each numeral is a complete, lighted cathode in the shape of the numeral. The cathodes are stacked so that different numerals appear at different depths to the viewer. The anode is a transparent metal mesh wrapped around the front of the display. The tube is filled with the inert gas neon with a small amount of mercury. When about 180 volts DC is applied between the anode and one of the ten cathodes, the gas near the cathode breaks down and glows with a warm orange color. L121_Nixie1.jpg (25141 Byte)

The Canola 121 was a breakthrough in technology and started a long line of Canon desktop calculators based on LSI circuits developed by Texas Instruments. Within two years the amount of electronics necessary for a desktop calculator was reduced to only a single-chip calculator circuit, some display drivers and the display itself. One of the drawbacks of the single-chip approach was the limited number of only 10-digits and we got a two-chip design again:

Type Year Digits Display technology Chip set
L121 1971 12 Nixie tubes TMC1733, TMC1753, TMC1754, TMC1807 
L100 1971 10 Panaplex style 
single tubes
TMC1737, TMC1753, TMC1754, TMC1807 
L100A 1971 10 Panaplex style TMS1824, TMS1825
L100S 1972 10 Panaplex style TMS0106 single chip
L121F 1972 12 Panaplex style TMS0201, TMS0302

The Canola 121F is the direct successor of this L121 adding a Constant key and a more advanced memory operation.

If you have additions to the above article please email: joerg@datamath.org.

Rick Bensene and Joerg Woerner, December 21, 2002. No reprints without written permission.