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Calculator CPU ICs: MDP1220C

 
Motorola? MDP1220C Calculator IC
ID: MPD1220C Used in: Toshiba BC-1287
Type: Calculator IC, 12+1 digit, switched constant, %, add-on (discount), square root, overflow recovery, sum of individual products/quotients, (switched) sum of individual totals and differences, mark-up/down, four function memory, switched floating/fixed modes, rounding modes.
Maker: Motorola?
Typical date range: Early 1980s
Package: 36 pin DIL (aka USA DIP)  black plastic
Date coding system: TBD
Notes: Designed for desktop financial calculators, drives VFD direct

Pin-outs and near example circuitry is shown for your information.  Please note - this is a back view.

Pins
D1-D13: display grid drivers
SA-SG and SDP: display segments and keyboard matrix
K0-K4: keyboard matrix
MIIL, MIL: memory indicators
CH, AC, CG: look like on-board oscillator
ER, MIIS: unknown

Voltages are given for this example respective to GND
VDD  -9V
VCC -29V

Notes: Lacks input overflow suppression but has overflow recovery
Interesting that the segment controls rather than the grid controls are used for part of the keyboard matrix.  This creates the need for 17 diodes in the matrix.  Second on-board memory is not used in the above circuit.