Has anyone found ordering information or the schematic referred to on Page 620 of Learning the Art of Electronics?
Page 620 of LAoE says, "The keypad is not a standard commercial part. See Appendix E for ordering information and Appendix 14N.20 for the schematic, in case you want to build your own."
However, Appendix E doesn't mention the keypad. The digital parts list on the LAoE website (link below) says, "See LAoE website" but there the trail goes cold; the website gives details for ordering the LCD but not the keypad (as far as I can see).
Also, Appendix 14N.20 doesn't seem to exist, nor the schematic for the keypad.
So the questions are:
Has anyone found ordering information for the LAoE keypad?
Has anyone found Appendix 14N.20 or the schematic for the keypad?
Can anyone suggest an alternative approach to providing the keypad functionality which includes: controlling lines D4 to D14 of an XC9572XL counter; and writing 8 bit values to RAM via a 74HC541 octal 3-state buffer.