| ??? 10/11/04 22:27 Read: times Msg Score: 0 +1 Good Answer/Helpful -1 Answer is Wrong |
#79164 - significant advantage in Hard UART Responding to: ???'s previous message |
Prahlad J. Purohit said:
I don't see any significant advantage in using Hard UART except for increased cost on hardware and size of hardware. Really??!! Consider this: If you have a hard UART, you need only access it once per character to extract the received character. A hardware UART samples the Rx line at sixteen times the bit rate - so an equivalent software UART would need to do the same. A standard 1 stop, 8 data, 1 start frame is a total of 10 bits. Thus a soft UART needs to sample the Rx line 160 times per character, as opposed to just once per character for a hard UART. And that's just sampling the line - you then need to evaluate each sample, decide whether you have a valid '1' or '0' bit, handle the start bit, handle shifting the serial Rx bits into a single character, etc, etc. Do you still see no significant advantage in using Hard UART?! With external UARTs, it gets even better: etc, etc, etc... I think you are definitely wrong on this one - there most certainly are significant advantages to be gained in using Hard UARTs! Of course, there's no such thing as a free lunch - so whether these advantages are justified in relation to the cost for a particular project is an entirely different matter! |
