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Ideally, the two ends of the cable will have a termination resistor connected across the two wires and two powered resistors to bias the lines apart when the lines are not being driven. The value of each termination resistor should be equal to the cable impedance (typically, 120 ohms for twisted pairs). Customers like the quality, performance, and value of the electronic cable. In this case, cable connections may be made to Serial 1 on either the 10-pin Serial Communications Header or the Serial 1 Connector. The SCK pin’s synchronous clock signal has configurable phase, polarity and baud rate so that it can interface to a variety of synchronous serial devices. Baud rates up to 56,000 baud are supported. Each serial port can be configured for the RS232 or RS485 protocol, and runs at standard baud rates up to 115,200 bits per second. We can gain insight into the operation of the RS232 protocol by examining the signal connections used for the primary serial port in the above table. It does not specify or recommend any data protocol. RS232 has numerous handshaking lines (primarily used with modems), and also specifies a communications protocol. In general if you are not connected to a modem the handshaking lines can present a lot of problems if not disabled in software or accounted for in the hardware (loop-back or pulled-up).

The PDQ Board, however, does not implement hardware handshaking. EIA standards where previously marked with the prefix "RS" to indicate recommended standard; however, the standards are now generally indicated as "EIA" standards to identify the standards organization. The recommended arrangement of the wires is as a connected series of point-to-point nodes, a line or bus. The EIA once labeled all its standards with the prefix "RS" (Recommended Standard), but the EIA-TIA officially replaced "RS" with "EIA/TIA" to help identify the origin of its standards. NOTE: The USA Swimming watermark will be removed or replaced by your organization logo. It is NOT necessary to introduce long delays in a network to avoid "data collisions." Because delays are NOT required, networks can be constructed, that will utilize the data communications bandwidth with up to 100% through put. While a multi-drop "type" application has many desirable advantages, RS422 devices cannot be used to construct a truly multi-point network.

While the standards bring uniformity to data communications, many areas are not specifically covered and remain as "gray areas" for the user to discover (usually during installation) on his own. RS232 has a maximum data rate of 115.2 kbps, while RS485 can operate at data rates of up to 10 Mbps. RS422 (differential) was designed for greater distances and higher Baud rates than RS232. The InitSPI() function provides a convenient way to initialize the SPI as the master at a 2MHz baud rate. A 2-wire synchronous IIC (Inter-IC) bus provides multi-drop signaling at rates up to 100 Kbaud. Regardless of the network, however, there are only four signals used: SCK provides a synchronized clock, MOSI and MISO signals are used for data transmission and reception, and /SS configures the QScreen as a master or slave device. RS423 is another single ended specification with enhanced operation over RS232; however, it has not been widely used in the industry. The specification allows for data transmission from one transmitter to one receiver at relatively slow data rates (up to 20K bits/second) and short distances (up to 50Ft. @ the maximum data rate). In its simplest form, a pair of converters from RS232 to RS422 (and back again) can be used to form an "RS232 extension cord." Data rates of up to 100K bits / second and distances up to 4000 Ft.

The RS232 signals are represented by voltage levels with respect to a system common (power / logic ground). The "idle" state (MARK) has the signal level negative with respect to common, and the "active" state (SPACE) has the signal level positive with respect to common. The connection between two or more elements (drivers and receivers) should be considered a transmission line if the rise and/or fall time is less than half the time for the signal to travel from the transmitter to the receiver. Any comments and/or corrections would be appreciated. Any number of characters can be sent, and the transmitter will automatically re-trigger with each new character (or in many cases a "bit-oriented" timing scheme is used in conjunction with network biasing for fully automatic operation, including any Baud rate and/or any communications specification, rs485 cable eg. Once a character is sent the hardware reverts back into a receive mode in about 1-2 microseconds (at least with R.E.