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Casio FX-7500G - hardware

The microprocessor HD62023 (Hitachi) or μPD1037 (NEC)

microprocessor HD62023/uPD1037

Pin functions

PinSymbol Function
1..16A0..A15 address bus
17WE bus write strobe signal, active low
18OE bus read strobe signal, active low
19..22FE, CS1..CS3 chip enable signals, active low
FE: ROM 32kB
CS3: RAM 8kB
23..30KI7..KI0 keyboard matrix input port, can be accessed through the KY register
31SW  
32TEST  
33VSS negative supply voltage rail
34VOSC Power supply for Clock
35VDD positive supply voltage rail
36,37OSCI, OSCO ceramic resonator 2.01MHz, OSCO is the output from the inverting oscillator amplifier
38..50KAC, KC0..KC11 keyboard matrix output port, controlled by the KY register
51..53INT2..INT0 interrupt inputs, unused, connected to VSS
54..61P0..P7 8-bit bi-directional port, can be accessed through the PD register
Function of individual bits:
62H1 4-bit output port, controlled through the PE register
63WENL connected to VSS
64..66H2, L1, L2 4-bit output port, controlled through the PE register
67
68
69
70
71
PRO
FR
LP
GC
DE
LCD driver control signals
72..79IO7..IO0 bi-directional data bus
80VSS negative supply voltage rail

The keyboard

The columns of the keyboard matrix are driven from the 13-bit output port KC. A pressed key makes contact between selected column and row. The rows are sensed by the 8-bit input port KI.

keyboard layout