MUX and DEMUX

[Kevin Weddle]

Why aren't multiplaxars and demultiplexars used for serial to parallel conversions? I understand that the operation of these devices could be used for conversions. Any help as to why would be appreciated. Are they used in chips to help complete these operations? I would like to see a communications project developed from these devices.

A multiplexar has select inputs. The select determines which input makes it to the output. If you continuously change the select, you have a parallel to serial conversion. This is what a computer does when it uses the parallel port to create an RS232 condition. Maybe you could use the ouptput of a counter to cycle the select. The input to the counter is a clock. I would be interested in an idea to use the parallel port to send the data and convert it to serial. Serial data was meant to send data at a rate much slower than parallel data. So that the microcontroller could handle other tasks while waiting on the slower data ouput. If you used just parallel on a slower device, you would have to wait anyways. So why not free up the microcontroller by sending the byte loaded into a register then access that byte with it's input to the multiplexar. That way you could send the byte and forget about it. Since the parallel data lines of a computer are always on, you have to send the data and still be able to change the data lines. That is why you load it into a register.