81 lines
2.0 KiB
Plaintext
81 lines
2.0 KiB
Plaintext
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(* Abbreviation: RS232Poll *)
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(* Version 1.10, Nov 1984 *)
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DEFINITION MODULE RS232Polling;
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(*
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Polled input/output via the RS-232 asynchronous
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serial port
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Since this module does not use interrupts, it is the
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responsibility of the programmer to poll (by calling
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'Read' or 'BusyRead') frequently enough to ensure that
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no characters are lost.
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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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*)
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EXPORT QUALIFIED
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Init, BusyRead, Read, Write;
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PROCEDURE Init (baudRate: CARDINAL;
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stopBits: CARDINAL;
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parityBit: BOOLEAN;
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evenParity: BOOLEAN;
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nbrOfBits: CARDINAL;
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VAR result: BOOLEAN);
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(*
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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
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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
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completed.
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The legal values for the parameters depend on the
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implementation (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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(*
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- Read a character from serial port, if one has been
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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, then ch = 0C, and
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received = FALSE.
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*)
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PROCEDURE Read (VAR ch: CHAR);
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(*
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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
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arrive.
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*)
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PROCEDURE Write (ch: CHAR);
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(*
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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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