3.2 Configuration Bits

The configuration bits of your device must always be set to appropriate values. It is unlikely your program will execute correctly, or at all, if these are not valid. You should consult your device data sheet to ensure that you understand the function of each configuration setting and the appropriate value that should be used.

You can use the MPLAB X IDE to assist in the creation of the code necessary to set the configuration bits, but any code it produces must be copied into a source file that is a part of your project.

CONFIG "WDTE=OFF"    // WDT Disabled; SWDTEN is ignored

As shown in the example code, you typically provide setting-value pairs to these directives, setting each configuration bit to the desired state, but an entire configuration word can also be programmed using one directive, if required. The CONFIG directive can also be used to set the device's IDLOC bits, where relevant.

Note that the setting-value pairs in the example code are quoted. This is to ensure that there can be no interaction between any predefined preprocessor macros (when the preprocessor is enabled) and the CONFIG directive data. It is recommended that quotes always be used.

If you are not using the MPLAB X IDE, the configuration bit settings and values associated with each device can be determined from an HTML guide. Open either the pic18_chipinfo.html guide for PIC18 devices or the pic_chipinfo.html guide for all other devices. These are located in the docs directory in the MPLAB XC8 C Compiler distribution that contains your PIC Assembler. Click the link to your target device and the page will show you the settings and values that are appropriate for your directives. Note that the usage examples shown in these HTML guides demonstrate the #pragma config directive used with C code as well as the CONFIG directive, for the PIC Assembler (shown above). Ensure you follow the “PIC-AS config Usage” examples.