Revision as of 01:45, 18 February 2013

Funktion

Compileranweisung zum Überschreiben der Standard-Taktfrequenz aus den BASCOM-Optionen.

Syntax

$CRYSTAL = var

Remarks

var	A numeric constant with the Frequency of the crystal.

The frequency is selectable from the Options Compiler Communication. It is stored in a configuration file. The $CRYSTAL directive overrides this setting.

It is best to use the $CRYSTAL directive as the used crystal frequency is visible in your program that way.

The $CRYSTAL directive only informs the compiler about the used frequency. It does not set any fuse bit. The frequency must be know by the compiler for a number of reasons. First when you use serial communications, and you specify $BAUD, the compiler can calculate the proper settings for the UBR register. And second there are a number of routines like WAITMS, that use the execution time of a loop to generate a delay. When you specify $CRYSTAL = 1000000 (1 MHz) but in reality, connect a 4 MHz XTAL, you will see that everything will work 4 times as quick.

Most new AVR chips have an internal oscillator that is enabled by default. Check the data sheet for the default value.

Example

$regfile = "m48def.dat"
$crystal = 4000000
$baud = 19200
 
Config Com1 = Dummy , Synchrone = 0 , Parity = None , Stopbits = 1 , Databits = 8 , Clockpol = 0
 
Print "Hello world"
End

Languages	English • Deutsch

@@ Line 1: / Line 1: @@
-== (**COPIED FROM ENGLISH PAGE**) === <span class="f_Header">Action</span><br/> =
+= <span class="f_Header">Funktion</span><br/> =
-Instruct the compiler to override the crystal frequency options setting.
+Compileranweisung zum Überschreiben der Standard-Taktfrequenz aus den BASCOM-Optionen.
 <span style="font-family: 'Arial';  color: #000000">&nbsp;</span>

$CRYSTAL/de

Revision as of 01:45, 18 February 2013

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