It seems normal to me.

Please note that, open drain means, it cannot source voltage.  For example,
if you connect one leg of an LED to this pin, and the other leg to resistor
and then to ground.  Then if you make the RA4 output and set the pin high
(1), the LED won't light up!  Any other pin with the same setting will light
the LED up, but not this pin, or an open drain pin.

RA4 is ALWAYS open drain, you do not make it open drain.

Regards,

Omer


-----Original Message-----
From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU] On
Behalf Of Lindy Mayfield
Sent: Friday, June 04, 2004 2:09 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [PICLIST] [PIC:] How to make pin RA4 on 16F877 I/O?

Marco,  It is the DS18S20, with 3 leads.

For some reason the examples in the book used 2 ports:  Porta 4 to pull down
the line, and Portb x to read the line.  I didn't know about A4 being
special open drain at the time, so I switched the code to B0 & B1, and it
still worked perfectly!  Which was why I asked if another pin could be
substituted for A4.

Is this normal?

Lindy

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