wait

Wait

Syntax:

Fixed Length Delay:

    Wait time units

Conditional Delay:

    Wait {While | Until} condition

Command Availability:

Available on all microcontrollers.

Explanation:

The Wait command will cause the program to wait for either a specified amount of time (such as 1 second), or while/until a condition is true.

When using the fixed-length delay, there is a variety of units that are available:

Unit	Length of unit	Delay range
us	1 microsecond	1 us - 65535 us
10us	10 microseconds	10 us - 2.55 ms
ms	1 millisecond	1 ms - 65535 ms
10ms	10 milliseconds	10 ms - 2.55 s
s	1 second	1 s - 255 s
m	1 minute	1 min - 255 min
h	1 hour	1 hour - 255 hours

At one stage, Great Cow BASIC variables could not hold more than 255. The 10us and 10ms units were added as a way to work around this limit. There is now no such limit (Wait 1000 ms will work for example), so these are not really needed. However, you may see them in some older examples or programs, and the 10us units are sometimes the shortest delay that will work accurately.

Warning

PIC Devices Only
MS Delays at Clock frequency’s below 28kHz are not supported and will silently fail.
US Delays at Clock frequency’s below 250kHz are not supported and will silently fail.
US Delays at lower Clock frequency’s is accurate ONLY when nn is divisible by 4. This is caused by the minimum ASM delay loop being a specific number of instructions.
US Delays at lower Clock frequency’ when not divisible by 4 will silently accept the nn value and incorrect delays will be produced.
Delays at Clock frequency’s below 500kHz may be impacted by previous instructions; testing of actual delays is advised.

Example:

    'This code will wait until a button is pressed, then it will flash
    'a light every half a second and produce a 440 Hz tone.

    #chip 16F819, 8

    #define BUTTON PORTB.0
    #define SPEAKER PORTB.1
    #define LIGHT PORTB.2
    Dir BUTTON In
    Dir SPEAKER Out
    Dir LIGHT Out

    'Assumes Button switches on when pressed
    Wait Until BUTTON = 1
    Wait Until BUTTON = 0

    Do
      'Flash the light
      Set LIGHT On
      Wait 500 ms
      Set LIGHT Off

      'Produce the tone
      '440 Hz = 880 changes = tone on for 1.14 ms
      Repeat 440
        PulseOut SPEAKER, 1140 us
        Wait 114 10us 'Wait for 114 x 10 us (1.14 ms)
      End Repeat
    Loop

For more help, see Conditions