At the risk of appearing stupid, since I didn't look at the datasheet first,
it looks like you would be trying to exceed the maximum current capability
of the port (whole device?).  The resistors (not considering LED on
resistance) would *consume* 5 milliamps.  The maximum output rating
(sourcing current) of the port (entire device?) is probably around 25
milliamps.  Therefore, trying to light more than 4 (5 * 5ma = 25ma) at a
time could result in this type of behavior.

That's my best guess for now.  I would suggest two things:

1) read the datasheet and find out what is legal

2) turn your led's around and connect them to Vss(Vcc).  Now write zero's to
the port to turn them on.  Most CMOS type devices can "sink" more current
than they can "source".

WARNING: DANGER: WARNING:

READ THE DATASHEET BEFORE TRYING #2.  YOU COULD END UP KILLING THE PIC BY
RUNNING TOO MUCH POWER THRU IT.

Good luck!  Hope this helps.

Michael Brown
Instant Net Solutions
www.KillerPCs.net

"In the land of the blind, he who has one eye is king"

----- Original Message -----
From: "Haris I. Volos" <pic@HIVOLOS.COM.CY>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Sunday, March 10, 2002 8:59 AM
Subject: [PIC]: 16F877 PORTD Can't run 8 LEDs simultaneously


> Hi! Another strange behaviour....
>
> I have connected 8 leds in series with 8 1K resistors respectively to
PORTD,
> the LEDs light at logic "1".
>
> RD0-------|>|---/\/\/\/\------GND
> ....            LED     1K
> RD7-------|>|---/\/\/\/\------GND
>
>
> If you light each LED alone its OK but if you try to light more than 4 the
> LEDs, RD0 and RD4 do not light even though that 5V are applied to the
LEDs.
> The voltage between the particular LED leads is 0.8V
> .
> I reduced the resistor to half and tried other LEDs but nothing, also I
> reset all TRISE bits (for the Paraller Port mode).
> I have read the datasheet but doesn't state anything.
>
> What do you thing?
>
> Thanks in advance,
>
> Haris
>
> --
> http://www.piclist.com hint: The PICList is archived three different
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>
>

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