http://en.wikipedia.org/wiki/Comparison_of_synchronous_and_asynchronous_signalling On Thu, Apr 2, 2009 at 12:12 AM, solarwind wrote: > On Wed, Apr 1, 2009 at 10:45 PM, Tony Vandiver > wrote: > > The ones with clocks are called synchronous because the clock transition > > syncronizes the behavior between the two systems, but protocols without > > a bus are asynchronous and generally use recognizable transitions on the > > data lines to synchronize along with a pre-negotiated timing that tells > > a uart for instance that it should expect so many bits in the time after > > the start bit, i.e. the systems without clocks depend on having a common > > time measurement and they expect the "bits" to be a certain width. > > That's why it's important to establish a baud rate for those kinds of > > systems where not so much for the I2C and SPI other than limiting the > > maximum detection frequency. Since there are likely never two systems > > with exactly the same clock rates, there is always an oversampling done > > on a UART to not just look at the signal received once during the > > expected bit time, but to sample 8 or more times, and assume that the > > dominant state is the one intended. That's a start anyway. > > Wow. Thanks. Asynchronous seems a lot more complicated. What is the > advantage of using an asynchronous system? Is USB asynchronous? > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist