81 lines
2.0 KiB
Plaintext
81 lines
2.0 KiB
Plaintext
(* Abbreviation: RS232Poll *)
|
||
(* Version 1.10, Nov 1984 *)
|
||
DEFINITION MODULE RS232Polling;
|
||
(*
|
||
Polled input/output via the RS-232 asynchronous
|
||
serial port
|
||
|
||
Since this module does not use interrupts, it is the
|
||
responsibility of the programmer to poll (by calling
|
||
'Read' or 'BusyRead') frequently enough to ensure that
|
||
no characters are lost.
|
||
|
||
Derived from the Lilith Modula-2 system developed by the
|
||
group of Prof. N. Wirth at ETH Zurich, Switzerland.
|
||
*)
|
||
|
||
|
||
EXPORT QUALIFIED
|
||
Init, 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 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, then ch = 0C, and
|
||
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 RS232Polling.
|
||
|