56 lines
1.8 KiB
Plaintext
56 lines
1.8 KiB
Plaintext
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DEFINITION MODULE RS232Polling;
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(*
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Polled 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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Since this module does not use interrupts, it is the responsibility
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of the programmer to poll (by calling 'Read' or 'BusyRead')
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frequently enough to ensure that no characters are lost.
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*)
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EXPORT QUALIFIED Init, 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 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 RS232Polling.
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