Chris Kuethe wrote: > On Thu, Mar 6, 2008 at 3:08 PM, Matthew Smith <[EMAIL PROTECTED]> wrote: > >> So my Trimble ACE II and Moto Oncore modules will tolerate RS232 levels >> without conversion? Are we absolutely sure on this - I don't want to >> fry anything! >> > > Well, I plugged my Oncore UT+ into my PC and it didn't work until I > put a level shifter in... no damage but no data either. So far I've > been lucky in that every device I tried that needed a level shifter > wasn't damaged by the lack of one. > > CK > > The powered down input resistance of a classic 1489 RS232 receiver is 3k minimum.
The classic 1488 RS232 driver has a 10mA short circuit current limit. To check if a 10mA current flowing in the CMOS output stage protection diodes compromises the long term reliability of the GPS receive can only be determined by consulting the datasheet for the CMOS output device. In any case, such currents flowing in the logic substrate may alter the chip timing and timing noise characteristics. For example when the inputs of a 74HC04 are overdriven the propagation delay and the associated timing jitter change significantly. Thus although the device may not fail anytime soon due to 10mA currents flowing in the input protection diodes, there is usually no guarantee that the chip will still operate correctly when significant protection network current is flowing. Bruce _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
