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In this case, cable connections must be made to Serial 1 at pins 5 and 6 of the 10-pin Serial Header or pins 7 and 8 on the 24-pin Field Header. In this case, cable connections may be made to Serial 1 on either the 10-pin Serial Communications Header or the Serial 1 Connector. Function prototypes for this function and other versatile serial I/O routines are defined in the COMM.H header file, and are described in detail in the Control-C Glossary. The default serial routines used by the onboard kernel assume that full duplex communications are available, so you cannot use the RS485 protocol to program the controller. Thus in Table 9 6 , RTS1 is connected to CTS1, and DSR1 is connected to DTR1 and DCD1 onboard the QScreen Controller using zero ohm shorting resistors. If you have not yet compiled the GETSTART program and you want to do the exercises here, open GETSTART.C in your TextPad editor, click on the Make Tool, and after the compilation is done, enter Mosaic Terminal by clicking on the terminal icon and use the "Send File" menu item to send GETSTART.DLF to the QScreen Controller.

Typing a carriage return at the terminal should now produce the familiar "ok" response via the Serial2 port. Also, several non-serial interrupts can stack up; if they have higher priority than the serial interrupts, they will be serviced before the Serial2 interrupt routine, and again a serial input or output bit may be lost. Also, in the diagram, the master’s /SS (slave select) is configured as an output. InitRS485() configures Port D to ensure that bit 5 is an output. RS232 uses inverse logic; that is, a positive bit at the 68HC11 UART is inverted by the onboard RS232 driver chip and appears as a negative signal on the serial cable. The DWOM bit (port D wired-or mode) should always be set to 0. Setting DWOM to 1 takes away the processor’s ability to pull the Port D signals high unless there is a pull-up resistor on each bit of the port. The standard C serial I/O routines such as printf(), scanf(), putchar(), and getchar() give you high level access to the serial ports. It is unquestionably an ideal choice for industrial equipment use due to its high speed, reliability, safety and versatility. Although many applications use RS-485 signal levels, the speed, format, and protocol of the data transmission are not specified by RS-485.

RS-485 signals are used in a wide range of computer and automation systems. It has Max.10 year of battery life and can cover a transmission range of 2km in urban scenes and 10km in line-of-sight scenes. Rather, it relies on software handshaking via transmission of XON/XOFF characters to coordinate data transfer and ensure that information is not lost when one of the communicating parties is busy. This setting is only relevant for the master device, as it is the master’s clock which drives the transfer. The communications is asynchronous because no synchronizing clock signal is transmitted along with the data. The QScreen Controller’s transmit data signal TxD1 (pin 2 on the 9-pin serial connector) is connected to the terminal’s receive data signal RxD (pin 2 on its 9-pin connector). Note that the data is changed by the transmitting device one half clock cycle before it is valid. In some cases, however, a sophisticated network may have device groups on a network that use different clock configurations. Please contact Mosaic Industries if you need these custom configurations. First you need to download the software.

Serial 2 is implemented by a software UART in the controller’s QED-Forth Kernel that uses two of the processor’s PortA I/O pins to generate a serial communications channel. Although the RS232 protocol specifies functions for as many as 25 pins, each communications channel requires only three for simple serial interfaces: TxD1 (transmit data), RxD1 (receive data), and DGND (digital ground). While these signals provide a data path, they do not provide hardware handshaking that allows the two communicating parties to let each other know when they are ready to send or receive data. Since both channels can operate simultaneously and independently, debugging can be performed while the application program is communicating via its primary channel. The secondary channel is very useful for debugging application programs that communicate with other computers or I/O via the primary channel. Data translation between different machines can be performed with ease, and applications that communicate via the primary serial port can be debugged using the secondary channel. The CPOL and CPHA bits configure the synchronous clock polarity and phase and specify when valid data is present on the MISO and MOSI data lines. Even though the MOSI pin is not connected to anything, the master initiates a transmission using a "dummy" byte.

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