What about reading 16 dip switchs and
no LCD? I need to read 16 bits of configuration
with no additional chip.
How much pins could I save?
What would be the minimum pin arrangement?

Octavio Nogueira
Tato Equipamentos Eletr=F4nicos Ltda
(11) 5506-5335
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nogueira@tato.ind.br                  ICQ# 19841898
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-----Mensagem original-----
De: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]
Em nome de Dennis Crawley
Enviada em: quarta-feira, 19 de mar=E7o de 2003 00:59
Para: PICLIST@MITVMA.MIT.EDU
Assunto: [PIC]:4x4&LCD in 1port


Hi all,
On  Feb 10 2002, Mike Rigby, Edson, Wouter, Dwayne, Jinx(don't you need
a haircut?=3D:), and many others, have proposed this challenge: to =
desing
a 4x4 matrix keyboard and LCD using only one port=3D 8 pins. Well, I =
have
read for fun that "three-days-ping-pong", and finally "the curiosity
killed the cat", so following Mike Rigby design I've arrived to a modest
solution
Features:
1.- Only 7 pins and lets free RB0.
2.- Use BF to detect internal operation. (saving an extra pin if it is
not
used)
3.- Only 8 diodes as extra components.
4.- Just take a look and tell me how to speed it up or generate a
decoder routine :)

Hard:
; The PortB is used as follows:
; RB0  FREE
; RB1  LCD ENABLE
; RB2  LCD R/W
; RB3  LCD RS
;              < LCD  DATA  BUS  >
;              D7    D6      D5  D4
;              |      |       |  |
; RB7 ---------o------|-------|--|---------|-,--|-,--|-,--|-,-
;              |      |       |  |        0|/  1|/  2|/  3|/
; RB6 --o------|------o-------|--|---------|-,--|-,--|-,--|-,-
;       |      |      |       |  |        4|/  5|/  6|/  7|/
; RB5 --|--o---|------|-------o--|---------|-,--|-,--|-,--|-,-
;       |  |   |      |       |  |        8|/  9|/  A|/  B|/
; RB4 --|--|---|--o---|--o----|--o---------|----|----|----|---
;      _|_ |  _|_ |  _|_ |   _|_ |        C|   D|   E|   F|
;      \ / |  \ / |  \ / |   \ / |         |    |    |    |
;      _V_ |  _V_ |  _V_ |   _V_ |         |    |    |    |
;       | _|_  | _|_  | _|_   | _|_        |    |    |    |
;       | \ /  | \ /  | \ /   | \ /        |    |    |    |
;       | _V_  | _V_  | _V_   | _V_        |    |    |    |
;       |  |   |  |   |  |    |__|_________|    |    |    |
;       |__|   |__|   |__|______________________|    |    |
;          |      |__________________________________|    |
;          |______________________________________________|


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