Disappearing Key Assignments

[ijabbott]

(01-02-2020 07:36 PM)Sylvain Cote Wrote:  

(01-02-2020 07:03 PM)ijabbott Wrote:  The 0s and 1s seem to be transposed, but apart from that it looks OK. Logic 0 is "asserted" (space) in RS-232, and logic 1 is "deasserted" (mark). The quiescent state of RXD and TXD (when no characters are being sent) is logic 1.

RS-232C use inverted logic vs voltage level, a logic zero is declared when the voltage goes over +3V and a logic 1 is declared when the voltage goes under -3V.

Yes, it's like a "double inversion". It is inverted with respect to voltage level and also inverted with respect to assertion:

• Negative = logic 1 = mark = deasserted
• Positive = logic 0 = space = asserted