An active signal state is often described as logic 1, on, true, or a mark.
An active state corresponds to the binary value 1, while an inactive state corresponds to the binary value 0. Signals can be in either an active state or an inactive state. For example, data is transmitted from the TD pin of the DTE to the RD pin of the DCE. The serial port pin and signal assignments are with respect to the DTE. The term "data set" is synonymous with "modem" or "device," while the term "data terminal" is synonymous with "computer." Table 8-1: Serial Port Pin and Signal Assignments Refer to the RS-232 standard for a description of the signals and pin assignments used for a 25-pin connector. The pins and signals associated with the 9-pin connector are described below. The pin assignment scheme for a 9-pin male connector on a DTE is given below. In fact, only three pins are required for serial port communications: one for receiving data, one for transmitting data, and one for the signal ground. However, most PC's and UNIX platforms use a 9-pin connection. To support these signal types, as well as the signal ground, the RS-232 standard defines a 25-pin connection. Serial ports consist of two signal types: data signals and control signals. Serial Port I/O (External Interfaces/API) External Interfaces/API
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