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Canon Canola L813 II

Date of introduction:  March 1982 Display technology:  Fluorescent
New price:   Display size:  8
Size:  6.3" x 5.2" x 1.8"
 159 x 132 x 45 mm3
    
Weight:  9.5 ounces, 269 grams Serial No:  445503
Batteries:  4*AA or NiCd Pack-5 Date of manufacture:  mth 08 year 1984
AC-Adapter:  AD-1 Origin of manufacture:  Japan
Precision:  8 Integrated circuits:  TMS1045 (___T8432)
Memories:  1 Displays:  Futaba 9-BT-18A
Program steps:   Courtesy of:  Joerg Woerner

At first glance looks this Canon Canola L813 II introduced in 1982 like its predecessor Canola L813 and even the keyplate states "Canon Canola L813". A closer examination of the two calculators reveals a slightly different functionality and keyboard layout, a typical sign of switching from one single-chip calculator circuit to another one during the life-cycle of the product. While the original Canola L813 uses a TMS1045 chip...

Dismantling the featured Canola L813 II calculator manufactured in August 1984 reveals a very cost effective design using a double-sided printed circuit board (PCB) centered around a - surprise, surprise - TMS1045 single-chip calculator circuit connected to a 9-digit Vacuum Fluorescent Display (VFD), a keyboard assembly using a flexible PCB and powered by 4 AA-sized alkaline batteries.

The TMS1045 is a member of the TMS1040 Product Family based on the TMS1070 "computer-on-a-chip" introduced in 1974 with the original TMS1000. While the TMS1070 can directly interface with low-voltage VFD up to 35 Volts does it still need external resistors and a zener diode to bias the anodes and grids of the display with respect to the filament. The TMS1040 added an extra VPP pin to connect a negative 30 Volts bias voltage for its modified output drivers. With the TMS1070 featuring 11 R Outputs for the Digits, 8 O Outputs for the Segments and 4 K Inputs for the Keyboard, reduced the TMS1040 the number of R Outputs to 9, consequently are all known TMS1040 calculator designs using a 9-digit VF Display.

Comparing the PCB of a Canola L813 manufactured in May 1978 with the PCB of this Canola L813 II from August 1984 reveals two almost identical designs and we are curious how Canon managed to change the functionality of the two calculators replacing the [+/-] and [RM], [CM] keys with [M+], [M-], and [RM/CM] keys. With our DCM-50A Platform allowing the Characterization of Single-Chip Calculator Circuits of the TMS1040 Family, we compared the two TMS1045 chips used on the PCBs to verify that they are 100% identical and the answer is pretty simple: Texas Instruments offered with most of their TMS1040 designs the calculator manufacturers a flexible menu to pick the desired functionality, meaning the chips would support both combined [C/CE] and [R/CM] keys or separate [C][CE] and [RM][CM] keys and the OEM would chose between them accordingly.

Layout of the Keyboard Matrices with their differences highlighted (Canola L813 and Canola L813 II):

  K1 K2 K4 K8 V K10
R0 (D1) [+420F] 0 6 +/−  
R1 (D2) [+420F] 1 7   M−=
R2 (D3) [+420F] 2 8   M+=
R3 (D4)   3 9    
R4 (D5) [+420F] 4 .    
R5 (D6)   5     =
R6 (D7)   CM RM RM/CM
R7 (D8) [Diode] + ÷ ×
R8 (D9) [ - AM]   CI   C

Notes: [y z] Sliding Switch Function, y Switch open, z Switch closed. K10 is a "virtual" 5th Keyboard Input line connected with two diodes to the K2 and K8 Keyboard Inputs of the TMS1045NL



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

Joerg Woerner, December 5, 2001. No reprints without written permission.