#MM74C923

Description: 20-key encoder

Datasheet: http://www.ti.com/lit/gpn/snMM74C923

Pinout:

    +-----------+
 Y1 |[ 1]   [20]| VCC
 Y2 |[ 2]   [19]| A
 Y3 |[ 3]   [18]| B
 Y4 |[ 4]   [17]| C
 Y5 |[ 5]   [16]| D
OSC |[ 6]   [15]| E
KBM |[ 7]   [14]| XOE
 X4 |[ 8]   [13]| DA
 X3 |[ 9]   [12]| X1
GND |[10]   [11]| X2
    +-----------+