81 lines
2.6 KiB
Plaintext
81 lines
2.6 KiB
Plaintext
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DEFINITION MODULE RS232Code;
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(*
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High-speed interrupt-driven input/output via the serial port
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Derived from the Lilith Modula-2 system developed by the
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group of Prof. N. Wirth at ETH Zurich, Switzerland.
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This module provides interrupt-driven I/O via the serial port,
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but the Interrupt Service Routine is implemented using in-line
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code (as opposed to IOTRANSFER).
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This approach is NOT portable to other Modula-2 implementations,
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but it allows for treatment of interrupts with high frequency.
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There is a buffer of at least 128 characters for received data.
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*)
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EXPORT QUALIFIED Init, StartReading, StopReading,
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BusyRead, Read, Write;
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PROCEDURE Init (baudRate: CARDINAL; stopBits: CARDINAL;
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parityBit: BOOLEAN; evenParity: BOOLEAN;
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nbrOfBits: CARDINAL; VAR result: BOOLEAN);
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(*- Initialize the serial port.
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in: baudRate transmission speed,
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stopBits number of stop bits (usually 1 or 2),
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parityBit if TRUE, parity is used, otherwise not,
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evenParity if parity is used, this indicates even/odd,
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nbrOfBits number of data bits (usually 7 or 8),
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out: result TRUE if the initialization was completed.
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The legal values for the parameters depend on the implementation
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(e.g. the range of supported baud rates).
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*)
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PROCEDURE StartReading;
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(*- Allow characters to be received from the serial port.
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This procedure initializes the communication controller to
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generate interrupts upon reception of a character. It also
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un-masks the corresponding interrupt level in the interrupt
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controller.
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*)
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PROCEDURE StopReading;
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(*- Disable receiving from the serial port.
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A call to this procedure disables the communication controller
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from generating interrupts. In addition it terminates the
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coroutine which listens to the line. The old interrupt vector
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as well as the old state of the interrupt controller (mask)
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is restored.
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*)
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PROCEDURE BusyRead (VAR ch: CHAR; VAR received: BOOLEAN);
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(*- Read a character from serial port, if one has been received.
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out: ch the character received, if any,
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received TRUE if a character was received.
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If no character has been received, ch = 0C, received = FALSE.
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*)
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PROCEDURE Read (VAR ch: CHAR);
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(*- Read a character from the serial port.
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out: ch the character received.
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As opposed to BusyRead, Read waits for a character to arrive.
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*)
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PROCEDURE Write (ch: CHAR);
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(*- Write a character to the serial port.
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in: ch character to send.
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Note: no interpretation of characters is made.
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*)
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END RS232Code.
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