ARM Technical Support Knowledge Articles


Applies to: C251 C Compiler



I'm trying to use extended bit variables in my C251 program and the compiler doesn't generate the correct code. Can you offer some suggestions?


You should first of all refer to page 107 in the 09.97 edition of the C251 manual for the correct way to declare bits in the extended area. In general, define extended bits as follows:

unsigned char ebdata variable1;
sbit bit1 = variable1 ^ 0;

Define external extended bits as follows:

extern bit ebdata bit1.

Do NOT define your external extended bits as follows:

extern bit bit1;

The above external declaration (extern bit bit1) does not tell the compiler that this bit is located in ebdata!

You will need C251 Version 2.14n and L251 Version 1.30 for extended bit variable support. Contact our technical support group for these files if you don't already have them.

Article last edited on: 2000-05-26 00:00:00

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