Inconsistent output on a 4x4 matrix keypad

[mister_e]

Alternative...

include "C:\PBP_PROG\INCLUDE_ROUTINES\KeyPad.bas"

define OSC 20
DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
DEFINE HSER_TXSTA 24h ' Enable transmit, BRGH = 1
DEFINE HSER_SPBRG 129 ' 9600 Baud @ 0.16%
DEFINE HSER_CLROERR 1 ' Clear overflow automatically

DEFINE KEYPAD_ROW        4        ' 4 ROW keypad       
DEFINE KEYPAD_ROW_PORT   PORTB    ' ROW port = PORTB
DEFINE KEYPAD_ROW_BIT    0        ' ROW0 = PORTB.4
DEFINE KEYPAD_COL        4        ' 4 COL keypad
DEFINE KEYPAD_COL_PORT   PORTB    ' COL port = PORTB
DEFINE KEYPAD_COL_BIT    4        ' COL0 = PORTB.0
DEFINE KEYPAD_DEBOUNCEMS 200      ' debounce delay = 200 mSec
DEFINE KEYPAD_AUTOREPEAT 1        ' use auto-repeat feature 

INTCON2.7=0
kKey    var byte

Start:
    @ READKEYPAD _kKey
    hserout ["Key=",dec kkey,13,10]
    goto start

Just modify the include to suite your requirement
kEYpAD.BAS... AVAILABLE BELLOW
http://www.picbasic.co.uk/forum/showthread.php?t=3250

and IN YOUR serout LINE...

SEROUT serpin,N2400,[#key,#B0]'Send key value out PortA.1

AND now that some know you experiment a Write/Read/Modify behaviour... use your existing code but modify it like

getkeyu:' Wait for all keys up
    LATB = 0 ' All output-pins low
    TRISB = $f0 ' Bottom 4-pins out, top 4-pins in
@   nop
    IF ((PORTB >> 4) != $f) THEN getkeyu'If keys down, loop
    PAUSE 50 ' Debounce key-input

getkeyp:' Wait for keypress
    FOR row = 0 TO 3 ' 4 rows in keypad
        LATB = 0 ' All output-pins low
        TRISB = (DCD row) ^ $ff ' Set one row pin to output
@       nop
        col = PORTB >> 4 ' Read columns
        IF col != $f THEN gotkey' If any keydown, exit
        NEXT row
    GOTO getkeyp ' No keys down, go look again

What happen now ?