PIC16f84 Question

[bryram67]

I am a newbie, please bear with me:

Can I have 5 inputs that when one is high, the corresponding output (5 outputs) is high and stays high until another input gets high? In other words the input will not stay high, but I want the output to stay high until a different input gets high. I know I need an interrupt, but a point in the right direction would be appreciated.

 

[ivancho]

You can do that. You can do it using interrupts, but you can't have 5 interrupt lines. There is an interrupt on the 16F877 that sets a flag each time PORTB pin7-pin4 changes.

You can also do something like this, suppose your 5 inputs are in PortB0-4 and your 5 outputs are at PortC0-4

INPUTS var byte
OUTPUTS var PortC

PortB = %00011111
PortC = %11100000

Start:

OldInputs = Inputs
INPUTS = PortB

If OldInputs <> INPUTS then
Outputs = INPUTS
endif

goto Start

Hope it helps

Ivancho

 

[motion]

Here is a sample coded in '84 assembly. It does not need interrupts and is probably just as fast.

PORTA_SAVE EQU 0Ch
TEMP_REG   EQU 0Dh

START:
    MOVLW   B'00011111'  ; MAKE ALL PINS INPUT
    TRIS    PORTA
    MOVLW   B'00000000'  ; MAKE ALL PINS OUTPUT
    TRIS    PORTB
;
    CLRF    PORT_SAVE
    CLRF    PORTB
LOOP:
    COMF    PORTA_SAVE,W
    MOVWF   TEMP_REG
    MOVF    PORTA,W
    MOVWF   PORTA_SAVE   ; SAVE FOR NEXT PASS
    ANDWF   TEMP_REG,W   ; DETECT RISING EDGE
    ANDLW   B'00011111'  ; MASK OUT UNUSED PINS
    BTFSS   STATUS,Z
    MOVWF   PORTB        ; OUTPUT TO PORT THE ACTIVE PIN
;
    GOTO    LOOP