PortB woes

After running the following piece of code, PORTB has the following value '11000000', even though I specifically clear them. What am I doing wrong or not doing. I am running this prog under sim. No devices added. The pic is a 16F887. Thanks.

banksel ANSELH
clrf ANSELH
banksel ANSEL
clrf ANSEL
clrf CM1CON0
clrf CM2CON1

banksel TRISA
clrf TRISA ;Now need to set ports on PortA to output

;banksel TRISB
BSF STATUS, 5
movlw B'11111000'
movwf TRISB ;Now need to set ports on PortB to input/output

;movlw h'60'
;movwf OSCCON

BCF OPTION_R,7 ;Enable internal pull-ups on PortB

banksel PORTA ;Return to bank0
CLRF PORTA ;Clear bits in PortA

;banksel PORTB
BCF STATUS, 5
nop
CLRF PORTB

What makes you think that value is wrong? You have bits 6 and 7 as inputs and WPUs on. I'm surprised you don't get 11110000.

BTW, it's always a good idea to post complete code as the error often lies elsewhere.

Mike.

Please excuse my ignorance, but if bits 4 and 5 are also input, why does PORTB not reflect the following - '11111000'. I get the previous result, even with pull ups disabled. I am trying to follow the logic in a 3x4 keypad tutorial. All code is listed below. Thanks.


;Equates Section
;**********************************************************************
;STATUS EQU 3 ;Used to switch banks
;PORTA EQU 5 ;To comm with outside world
;PORTB EQU 6
;TRISA EQU 85H ;Used to set pins on port to input or output
;TRISB EQU 86H
OPTION_R EQU 81H ;This option handles the pull-ups

;**********************************************************************

PROCESSOR 16f887 ; list directive to define processor
#include <p16f887.inc> ; processor specific variable definitions


; '__CONFIG' directive is used to embed configuration data within .asm file.
; The labels following the directive are located in the respective .inc file.
; See respective data sheet for additional information on configuration word.

__CONFIG _CONFIG1, _LVP_OFF & _FCMEN_ON & _IESO_OFF & _BOR_OFF & _CPD_OFF & _CP_OFF & _MCLRE_ON & _PWRTE_ON & _WDT_OFF & _INTRC_OSC_NOCLKOUT
__CONFIG _CONFIG2, _WRT_OFF & _BOR21V

;***** VARIABLE DEFINITIONS (examples)

Cblock 0x20 ; First free RAM location
endc ; No variables


;**********************************************************************
RESET_VECTOR CODE 0x0000 ; processor reset vector
nop
goto Start ; go to beginning of program

INT_VECTOR CODE 0x0004 ; interrupt vector location
pagesel Start
goto Start


;MAIN_PROG

;Config Section
Start
;bsf STATUS, 5 ;Turns to bank1. Note that bit 5 in the SFR Status is
;RP0. RP0 and RP1 together determine which bank is selected,
;eg RP1 RP0 Bank
; 0 0 0
; 0 1 1 etc.


banksel ANSELH
clrf ANSELH
banksel ANSEL
clrf ANSEL
clrf CM1CON0
clrf CM2CON1

banksel TRISA
clrf TRISA ;Now need to set ports on PortA to output

;banksel TRISB
bsf STATUS, 5
movlw B'11111000'
movwf TRISB ;Now need to set ports on PortB to input/output

;movlw h'60'
;movwf OSCCON

;bcf OPTION_R,7 ;Enable internal pull-ups on PortB

banksel PORTA ;Return to bank0
CLRF PORTA ;Clear bits in PortA

;banksel PORTB
bcf STATUS, 5
nop
CLRF PORTB ;Clear bits in PortB

;Program starts now
Column1
;{

clrf PORTB
bsf PORTB,0
bcf PORTB,1
bcf PORTB,2

;}

Check_Key1
;{

btfss PORTB,3 ;Check if bit 3 of PortB is clear
goto Check_Key4 ;Key 1 not pressed
movlw d'1' ;Key 1 was pressed
movwf PORTA ;Display a '1' on LEDs

;}

Check_Key4

;{
btfss PORTB,4 ;Check if bit 4 of PortB is high(=1)
goto Check_Key7 ;Key 4 not pressed
movlw d'4' ;Key 4 was pressed
movwf PORTA ;Display a '4' on LEDs

;}

Check_Key7

btfss PORTB,5 ;Check if bit 5 of PortB is high
goto Check_Key10 ;Key 7 not pressed
movlw d'7' ;Key 7 was pressed
movwf PORTA ;Display a '7' on LEDs

Check_Key10

btfss PORTB, 6 ;Check if bit 3 of PortB is clear
goto Column2 ;Key 10 not pressed
movlw d'10' ;Key 10 was pressed
movwf PORTA ;Display a '1' on LEDs

;*************************************************************

Column2

clrf PORTB
bcf PORTB, 0
bsf PORTB, 1
bcf PORTB, 2

CHECK_KEY2
btfss PORTB, 3 ;Check if bit 3 of PortB is clear
goto CHECK_KEY5 ;Key 2 not pressed
movlw d'2' ;Key 2 was pressed
movwf PORTA ;Display a '1' on LEDs

CHECK_KEY5
btfss PORTB, 4 ;Check if bit 3 of PortB is clear
goto CHECK_KEY8 ;Key 5 not pressed
movlw d'5' ;Key 5 was pressed
movwf PORTA ;Display a '1' on LEDs

CHECK_KEY8
btfss PORTB, 5 ;Check if bit 3 of PortB is clear
goto CHECK_KEY11 ;Key 8 not pressed
movlw d'8' ;Key 8 was pressed
movwf PORTA ;Display a '1' on LEDs

CHECK_KEY11
btfss PORTB, 6 ;Check if bit 3 of PortB is clear
goto COLUMN3 ;Key 10 not pressed
movlw d'11' ;Key 10 was pressed
movwf PORTA ;Display a '1' on LEDs
;************************************************************

COLUMN3

clrf PORTB
bcf PORTB, 0
bcf PORTB, 1
bsf PORTB, 2

CHECK_KEY3
btfss PORTB, 3 ;Check if bit 3 of PortB is clear
goto CHECK_KEY6 ;Key 3 not pressed
movlw d'3' ;Key 3 was pressed
movwf PORTA ;Display a '1' on LEDs

CHECK_KEY6
btfss PORTB, 4 ;Check if bit 3 of PortB is clear
goto CHECK_KEY9 ;Key 6 not pressed
movlw d'6' ;Key 6 was pressed
movwf PORTA ;Display a '1' on LEDs

CHECK_KEY9
btfss PORTB, 5 ;Check if bit 3 of PortB is clear
goto CHECK_KEY12 ;Key 9 not pressed
movlw d'9' ;Key 9 was pressed
movwf PORTA ;Display a '1' on LEDs

CHECK_KEY12
btfss PORTB, 6 ;Check if bit 3 of PortB is clear
goto Column1 ;Key 12 not pressed
movlw d'12' ;Key 12 was pressed
movwf PORTA ;Display a '1' on LEDs
goto Column1 ;Do this forever


END ; directive 'end of program'

I only got to the 5th instruction before I found the first error,

I personally don't like the banksel macro as it wastes a lot of space and I prefer to keep track of banking myself. So I would write,

Also, when posting code use the code tags. Type [code] before your code and [/code] after it.

Mike.

I don't see the problem... Runs ok in ISIS, even with that small error...