Pins
A, B, C, D, E, F, G, PI (inverted): display segments and decimal point
D1 to D9: display grid signal for each digit, and keyboard multiplexing
C (inverted, boxed): cancel key
K (inverted, boxed): unsure, either constant enabled or constant key
KN, KF (boxed): keyboard multiplex lines, the other lines are supplied by D1 to D9
OSC1-3: on board oscillator
FDp To0: unknown (could be floating/fixed decimal point to zero)

Notes:
No input overflow suppression
Negative zero bug
Pseudo fixed decimal bug
Extended divide to negative zero bug
Seven digit results for division
Constant on multiply and divide only

VGG -12V
VDD -6V
GND 0V