Ax51 User's Guide
REGUSE Assembler Directive
REGUSE function (register | range 〚,
register | range〛)
The REGUSE directive specifies which registers are modified
by the specified function. The function
specified must match the symbol name used in a PUBLIC
The registers specified by the REGUSE directive are used by
global register optimization to improve the performance of C
functions that call assembler routines.
The registers that may be specified are:
The range specifies a range of registers such as
Refer to Interfacing
C to Assembler in the Cx51 User's Guide. The section Register
Usage contains additional information about the registers that
can be altered in assembler routines.
The assembler does not verify the registers used in a routine.
Make certain you are careful to specify the correct set of
registers used. Failure to do so will result in run-time problems
(due to overwritten register values).
The function name specified must exactly match the
spelling and case of the identifier defined in the assembly source
file. If the CASE directive was not specified, identifiers
are converter to uppercase.