In that case, do not install jumper caps at the jumpers labeled "Term" or "RTerm". Resistive termination - If the PDQ Board is at the end of the RS485 cable you can terminate the cable by installing jumper caps at both jumper locations, "Term" and "RTerm". No termination - If the PDQ Board is not an end device, you should not terminate that cable. In this case, cable connections may be made to Serial 2 on either the 10-pin PDQ Board Serial Communications Header, or the Docking Panel’s 10-pin right-angle Serial Header, or the Docking Panel’s Serial2 DB-9 Connector. In this case, cable connections may be made to Serial 2 at pins 4 and 10 of the PDQ Board’s 10-pin Serial Header, or pins 5 and 6 of the Docking Panel’s 10-pin right-angle Serial Header. In this case, cable connections may be made to Serial 1 on either the 10-pin PDQ Board Serial Communications Header, or the Docking Panel’s 10-pin right-angle Serial Header, or the Docking Panel’s Serial1 DB-9 Connector. There are surface-mount resistor pads on the Docking Panel to bring out the RS485 signals to the DB9 Serial 1 Connector. There are different families of products on the market: instruments which measure a single electrical parameter (voltage, current, frequency, and phase angle cosϕ), generally used in single-phase systems, as instrumentation on the machine, and instruments allowing all the electrical parameters to be measured and displayed, both for the single-phase system and for the three-phase system.

Of the processor’s three synchronous SPI (Serial Peripheral Interface) ports, two are available for inter-processor communications on multi-processor systems, and the third is brought out to the Wildcard expansion bus. RS485 is the preferred serial communications standard for long distance industrial communications. 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. The Serial 1 and Serial2 ports can be configured for either RS-232 or RS-485 communications at standard baud rates up to 115200 bits per second. The M bit, with mask 0x10, determines whether eight or nine bits total are transmitted with each byte, regardless of whether or not the most-significant bit is a parity bit. The PDQ Board's two serial ports support limited use of generating a parity bit. The rubber buttons offer limited liquid resistance while the wall mount unit can be for indoor use as the 720 SM, shown below or, mounted in a weather resistant enclosure - 720 SMO. Receiver Input Resistance (Ohms), (1 Standard Load for RS485) 3k to 7k 4k min. These 9-pin standard DB-9 serial connectors are located on the back of the Docking Panel. The pinout of the PDQ Board’s Communications Header (H2), Docking Panel’s Communications Header (H1), and the Docking Panel’s Communications DB-9 Connectors are shown in the following tables.

Contact Mosaic if you require RS485 signals to be routed to the DB-9 Connector. Please contact Mosaic Industries if you need this custom configuration. If your computer does not have an RS232 serial port, low cost USB-to-RS232 serial cables are available; contact Mosaic Industries for details. The PDQ Single Board Computer (SBC) has two asynchronous serial communications ports named Serial1 and Serial2. For those of you interested in the details, here’s how it works: The low-level serial driver routines named Key(), AskKey() and Emit() are revectorable routines that can be redirected to use either of the serial ports. Two asynchronous communications ports named Serial1 and Serial2 can each be configured for RS232 or RS485 protocols. The Serial1 and Serial2 ports are is supported by the HCS12's dual on-chip hardware UARTs, and do not require interrupts to work properly. The Serial ports are implemented by the dual on-chip hardware UARTs (Universal Asynchronous Receiver/Transmitters) on the Freescale 9S12 (HCS12) microcontroller. The primary and secondary serial communications ports are accessible through the PDQ Board's 10 pin, dual row Communications Header (H2) and through the Docking Panel's 10 pin, right-angle, dual row Communications Header (H1) and individual DB-9 Serial 1 and Serial 2 connectors.

By default, the RS485 connections are not brought out to the Docking Panel’s DB-9 Serial1 Connector, although custom placement of zero-ohm surface-mount resistors on the Docking Panel can route the RS485 signals to the DB-9. Serial1 port the default startup serial link. Each UART (sometimes referred to as a "USART") controls the serial-to-parallel and parallel-to-serial conversion and performs all of the timing functions necessary for one asynchronous serial communications link. The words port and channel are used interchangeably to refer to a serial communications link. These protocols are summarized on this page, but for more information regarding their data formats and their use for simplex or multi-drop serial lines, consult Understanding Serial Communications (but keep in mind that that page is directed to the use of the UART Wildcard, so it uses different driver functions). This page describes the serial ports and how to use them for instrument control and automation applications.