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RS-232 interface: Difference between revisions
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Related ITU-T standards include V.24 (circuit identification) and V.28 (signal voltage and timing characteristics). | Related ITU-T standards include V.24 (circuit identification) and V.28 (signal voltage and timing characteristics). | ||
The RS-232 standard defines the voltage levels that correspond to logical one and logical zero levels for the data transmission and the control signal lines. Valid signals are either in the range of +3 to +15 volts or the range −3 to −15 volts with respect to the "Common Ground" (GND) pin; consequently, the range between −3 to +3 volts is not a valid RS-232 level. For data transmission lines (TxD, RxD, and their secondary channel equivalents), logic one is defined as a negative voltage, the signal condition is called "mark". Logic zero is positive and the signal condition is termed "space". Control signals have the opposite polarity: the asserted or active state is positive voltage and the deasserted or inactive state is negative voltage. Examples of control lines include request to send (RTS), clear to send (CTS), data terminal ready (DTR), and data set ready (DSR). | |||
{| class="wikitable" | |||
|+ RS-232 logic and voltage levels | |||
! Data circuits !! Control circuits !! Voltage | |||
|- | |||
| 0 (space) || Asserted || +3 to +15 V | |||
|- | |||
| 1 (mark) || Deasserted || −15 to −3 V | |||
|} | |||
''(Incorporates text from https://en.wikipedia.org/wiki/RS-232)'' | |||
[[Category:Interfaces]] | [[Category:Interfaces]] | ||