=20 Jason White wrote: > Hello everyone, > > My work has a product that has four pins for RS232, RS485, or RS422. > Previously the product was built as either RS232 or RS485/RS422 - only > containing a transceiver for one or the other but not both. But now we > want to make a product that can be electronically configured as one or > the other. The problem is that the same pins are used for each > interface! > > I was wondering if anybody has any suggestions for a circuit that > would permit the either of the transceivers (232 and 422) to be > disconnected from the circuit - so that only one was physically > connected to the pins at a time. Off the top of my head I can think of > two solutions: > > (1) Signal relays on the input/output of each transceiver. This would > permit the 232/422/485 to be on the same pins. > Pros: Robust > Cons: bulky, power hungry, and expensive. > > (2) Electronic switch, would a CD4066B work? An electronic switch is > desirable but many don't handle the voltages required. For instance > the MAX232 tolerates +/-30V whereas the seemingly obsolete CD4066B > only handles 0-15V, requiring protection. > Pros: Smaller > Cons: Not sure how to implement, inadequate voltage tolerance There's already a lot of great suggestions in this thread. But, if=20 you're still in doubt and want to use an analog switch: Selecting the Right CMOS Analog Switch pdfserv.maximintegrated.com/en/an/AN5299.pdf Thank you, 73, --=20 Don Kuenz KB7RPU There was a young lady named Bright Whose speed was far faster than light; She set out one day In a relative way And returned on the previous night. --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .