----- Original Message ----- From: "Russell McMahon" To: "Microcontroller discussion list - Public." Sent: Friday, May 13, 2005 1:07 PM Subject: Re: [PIC] RS232, USART, and COM > > Why does pc com port use RS232, is there a standard that requires > > this. > > On the other hand, why do the pics use uart without rs232, is this > > a pic problem which will make it more complex to connect to pc? > > RS232 is intended for intercommunication between pieces of equipment > over distances liable to be found in a computer room. The interface is > intended to be reasonably robust and reasonably well protected against > real world conditions. > > Inter-Integrated circuit interfacing is done at a level that makes > most sense for the technology in use, whether TTL, CMOS, ECL or > whatever. The interfaces are (hopefully) robust enough for their > intended on-PCB environment. It would make little sense to invariably > engineer them for "real world" environments - especially so when many > are used only within the PCB environment. > > When there is a need to transfer signals between real-world and PCB > environments suitably engineered interfaces are provided. These may be > simple and passive and use only eg resistors and capacitors or may be > more complex and may use special ICs or isolation equipment. When it > is necessary for a PIC (or any other processor) to talk RS232 an RS232 > interface is added. similarly RS422, 20 mA current loop or any other > specific standard interface. If a PIC was equipped with an RS232 > interface and one wanted to use RS422 it would be even more annoying > than it is now to do so. > > Using the right thing in the right place and knowing which is which is > part of what engineering is about. > I do understand now, i.e. RS232 is usefull to extend the u(s)art interface over a long distance, i.e. 1 or 2 or 3 meters, but when our signals travel only a few centimeters on a pcb, we do not need rs232 and in fact rs232 will simply be a hinderance. tnx > > > Russell McMahon > > > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > > > -- > No virus found in this incoming message. > Checked by AVG Anti-Virus. > Version: 7.0.308 / Virus Database: 266.11.9 - Release Date: 12/05/2005 > > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist