Ah the beauty of old conventions. I could not understand why RS232 treated -ive voltages as 1s and +ive voltages as 0s. But, I got a bit of an explanation from a tech support person and then wikipedia:
http://en.wikipedia.org/wiki/RS-232
Turns out RS232 was created in the days of teletype machines (YEAH!). In those days trasmitted data was stored as holes punched onto moving tape. These holes were then read as 1s and no holes were read as zeros. So the translation was that a hole (i.e. lack of paper and bit value 1) makes sense as a -ive voltage and no hole (i.e. still paper and bit value 0) makes sense as a +ive voltage.
This all reminds me of that story as to how the wheel spacing of Roman chariots set constraints for getting rocket ships onto the launch pad.
http://www.astrodigital.org/space/stshorse.html
Makes perfect sense now!
http://en.wikipedia.org/wiki/RS-232
Turns out RS232 was created in the days of teletype machines (YEAH!). In those days trasmitted data was stored as holes punched onto moving tape. These holes were then read as 1s and no holes were read as zeros. So the translation was that a hole (i.e. lack of paper and bit value 1) makes sense as a -ive voltage and no hole (i.e. still paper and bit value 0) makes sense as a +ive voltage.
This all reminds me of that story as to how the wheel spacing of Roman chariots set constraints for getting rocket ships onto the launch pad.
http://www.astrodigital.org/space/stshorse.html
Makes perfect sense now!
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