DEFINITION MODULE RS232Int; (* Interrupt-driven input/output via the serial port Derived from the Lilith Modula-2 system developed by the group of Prof. N. Wirth at ETH Zurich, Switzerland. Interrupts are treated with the standard procedure IOTRANSFER. Received characters are stored in a buffer of 100H characters. The module initializes the serial port as follows: baudRate = 1200, stopBits = 1, parityBit = FALSE, evenParity = don't care, nbrOfBits = 8 *) EXPORT QUALIFIED Init, StartReading, StopReading, BusyRead, Read, Write; PROCEDURE Init (baudRate: CARDINAL; stopBits: CARDINAL; parityBit: BOOLEAN; evenParity: BOOLEAN; nbrOfBits: CARDINAL; VAR result: BOOLEAN); (*- Initialize the serial port. in: baudRate transmission speed, stopBits number of stop bits (usually 1 or 2), parityBit if TRUE, parity is used, otherwise not, evenParity if parity is used, this indicates even/odd, nbrOfBits number of data bits (usually 7 or 8), out: result TRUE if the initialization was completed. The legal values for the parameters depend on the implementation (e.g. the range of supported baud rates). *) PROCEDURE StartReading; (*- Allow characters to be received from the serial port. This procedure initializes the communication controller to generate interrupts upon reception of a character. It also un-masks the corresponding interrupt level in the interrupt controller. *) PROCEDURE StopReading; (*- Disable receiving from the serial port. A call to this procedure disables the communication controller from generating interrupts. In addition it terminates the coroutine which listens to the line. The old interrupt vector as well as the old state of the interrupt controller (mask) is restored. *) PROCEDURE BusyRead (VAR ch: CHAR; VAR received: BOOLEAN); (*- Read a character from serial port, if one has been received. out: ch the character received, if any, received TRUE if a character was received. If no character has been received, ch = 0C, received = FALSE. *) PROCEDURE Read (VAR ch: CHAR); (*- Read a character from the serial port. out: ch the character received. As opposed to BusyRead, Read waits for a character to arrive. *) PROCEDURE Write (ch: CHAR); (*- Write a character to the serial port. in: ch character to send. Note: no interpretation of characters is made. *) END RS232Int.