Here's all I have. There are no active components in the circuit. Just one LED. The I/O will source/sink 25mA automatically. Again, the code and the built circuit works fine at 4.3V and above. I can see the LED turning ON and OFF at a visible rate. I can apply 3V to Vdd but I get nothing, 0V, at the I/O port being tested.
There is no segment display. Just one LED.
Code
STATUS equ 03h ;Address of the STATUS register
TRISA equ 85h ;Address of the tristate register for port A
PORTA equ 05h ;Address of Port A
COUNT1 equ 21h ;First counter for our delay loops
COUNT2 equ 22h ;Second counter for our delay loops
bsf STATUS,5 ;Switch to Bank 1
movlw 00h ;Set the Port A pins
movwf TRISA ;to output.
bcf STATUS,5 ;Switch back to Bank 0
Start movlw 1Fh ;Turn the LED on by first putting
movwf PORTA ;it into the w register and then
Loop1 decfsz COUNT1,1 ;Subtract 1 from 255
goto Loop1 ;If COUNT is zero, carry on
decfsz COUNT2,1 ;Subtract 1 from 255
goto Loop1 ;Go back to the start of our loop.
;This delay counts down from
;255 to zero, 255 times
movlw 00h ;Turn the LED off by first putting
movwf PORTA ;it into the w register and then on
Loop2 decfsz COUNT1,1 ;This second loop keeps the
goto Loop2 ;LED turned off long enough for
decfsz COUNT2,1 us to see it turned off
goto Loop2
goto Start ;go back to Start and turn LED
END
Thanks