PIO.exp

MODULE PIO;
IMPORT SYSTEM;
    CONST
        gpio = -32;
        gpoc = -28;

    PROCEDURE del(i : INTEGER);
    BEGIN
        REPEAT
            DEC(i)
        UNTIL i = 0
    END del;

    PROCEDURE Send*(x : LONGINT);
        VAR
            i: INTEGER;
    BEGIN
        FOR i := 0 TO 7 DO
            SYSTEM.PUT(gpio, x MOD 2+2);
            del(60);
            SYSTEM.PUT(gpio, x MOD 2);
            del(25);
            x := x DIV 2
        END;
        SYSTEM.PUT(gpio, 0);
        del(100)
    END Send;

    PROCEDURE Receive*(VAR x : LONGINT);
        VAR
            i: INTEGER;
            x0: INTEGER;
    BEGIN
        x0 := 0;
        REPEAT
        UNTIL ~ SYSTEM.BIT(gpio, 2);
        FOR i := 0 TO 7 DO
            SYSTEM.PUT(gpio, 2);
            del(60);
            IF SYSTEM.BIT(gpio, 2) THEN
                x0 := x0+0100H
            END;
            SYSTEM.PUT(gpio, 0);
            del(25);
            x0 := ROR(x0, 1)
        END;
        x := x0
    END Receive;

    PROCEDURE Reset*;
    BEGIN
        SYSTEM.PUT(gpio, 0);
        SYSTEM.PUT(gpoc, 3)
    END Reset;

BEGIN
    Reset()
END PIO.