On 5 Feb 2006 at 9:43, Phil Keller wrote:

>   Has anyone actually measured the Vol vs Iol?

Hi Phil,

You can approximate the output stage of a PIC running at 5 volts as 
35 ohms when sinking and 75 ohms when sourcing. As you 
approach 25 mA when sourcing, expect the resistance to increase 
rapidly and it becomes a constant (unknown amount of) current.

What does this mean? Generally it means that if you are trying to 
get a lot of current out of a PIC pin, and you are setting and clearing 
pins, there is a greater chance you'll get into trouble because of the 
"read-modify-write" problem. If you are driving a pin really hard, 
maybe it'll be read as low when it's actually high, and vice versa.

So if you really need 25 mA, it's best to address the pins as a full 
port.

Cheerful regards,

Bob
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