C51: Signed Bit Field Not Supported

Information in this article applies to:

• C51 All Versions

QUESTION

I have problems using signed bit fields.

Are signed bit fields not supported by Keil C51?

ANSWER

Per ANSI standard, the behavior on bit fields is implementation-specific. In Keil C51, bit fields are always unsigned. There is no way to define signed bit fields.

Bit fields are inefficient on an 8051. With an 8051, you should use bdata addressable objects.

MORE INFORMATION

• Refer to Bit-Addressable Objects in the Cx51 User's Guide.
• Refer to sbit in the Cx51 User's Guide.

SEE ALSO

• C51: Bit Field Unions Don't Work as Expected
• C51: Order of Bitfields
• C: C Standards
• C51: Bit Field Unions Give Strange Results

Last Reviewed: Thursday, February 25, 2021