David Cary wrote: > > [tiny nit-pick] > > James Paul on 2001-06-13 08:44:56 AM claimed that > > And as far as the PIC pin is concerned, it's general knowledge that > > a TTL/CMOS output is better at sinking current than at sourcing it. > > Yes, everyone knows this. However, everyone is wrong :-/. > > All the CMOS devices I work with have exactly the same current sink as current > source. > > For example, > the PIC16F7X data sheet > http://www.microchip.com/0/lit/pline/picmicro/families/16f7x/index.htm > > http://www.microchip.com/download/lit/pline/picmicro/families/16f7x/devices/16f77/30325a.pdf > says, on the first page, > High Sink/Source Current: 25 mA > . > > I would be surprised to learn of any PIC output that had a significant > difference in current sink vs. current source (except for ``open drain'' pins > like RA4). > > -- > David Cary > electronics nit-picker Looking deeper into the PDF spec you reference, page 125 clarifies the 25mA sink/source as the MAXIMUM from any pin, not the typical. I also find (on page 129) the VOL is given as 0.6V @ 8.5mA while the VOH is given as VDD-0.7V @ -3.0mA. This indicates that the "pullup" transistor can not provide the same current as the "pulldown" for a given voltage difference from the power rail. Indeed, I would expect the VOH level to drop even further if providing -8.5mA. Based upon these specs, I would tend to agree with James Paul statement. David W. Gulley (another nit-picker) -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body