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In this case, cable connections may be made to Serial 1 at pins 5 and 6 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 other words, each local UART on the wildcard can both send data to and receive data from a remote UART on the other end of a connecting serial cable. The Serial ports are implemented by the dual on-chip hardware UARTs (Universal Asynchronous Receiver/Transmitters) on the Freescale 9S12 (HCS12) microcontroller. The hardware detects the start-bit of the transmission and automatically enables (on the fly) the RS485 transmitter. A jumper labeled "2 485En" (J7) enables RS485 operation on the Serial2 port if the jumper cap is installed, and configures Serial2 for RS232 operation if the jumper cap is not installed. Below are the specifications for RS232, RS423, RS422, and RS485. Owing to hardware constraints, if modem handshaking is needed on UART channel 1, then channel 1 must be configured for RS232, and channel 2 cannot be configured for RS232 communications.

The most widely used protocol is RS232, a full duplex protocol with a single-ended bipolar voltage swing on the serial cable. 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. Likewise, the terminal’s transmit signal /TxD is connected to the PDQ Board’s receive signal /RxD1. 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. Bias termination - Using resistive termination decreases noise immunity, particularly if the cable is loaded with many devices. If you do this now, remember to move the QScreen Controller’s serial connector back to Serial Port 1, and to change the terminal’s baud rate back to 19200 baud using the "Comm" item under the terminal’s "Settings" menu. Once a character is sent the hardware reverts back into a receive mode in about 1-2 microseconds (at least with R.E.

All of the RS232 signals start with the / (slash, pronounced not) character to indicate that the signals on the serial cable are logically inverted. A logic-low start bit marks the start of a character, followed by 5 to 8 data bits per character. The BAUD routine described at the start of this subsection configures the baud rate of each of the Serial1 and Serial2 channels. Pre-coded device drivers configure the SPI for a standard data format, and it is easy to customize a data format and baud rate for your application. 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. If this limitation is not a problem, you can reverse the roles of the Serial1 and Serial2 ports, because they have identical communications capabilities. Two asynchronous communications ports named Serial1 and Serial2 can each be configured for RS232 or RS485 protocols. 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. From the PDQ Board’s point of view, these three signals (/TxD, /RxD, and ground) are the only connections required to perform serial communications.

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. SERIAL.h header file, and are described in detail in the C Glossary. The default serial routines used to download programs to the operating system assume that full duplex communications are available, so you cannot use the RS485 protocol to program the controller. 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. 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. The UART Wildcard implements these optional RS232 modem handshaking signals on channel 1. The handshaking signals can be disabled and/or ignored by applications that do not need them. RC termination - In some applications requiring low power you may not want to load the line with 120 Ω resistors at each end. This page describes the serial ports and how to use them for instrument control and automation applications.

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