Fractional Arithmetic

Many of the intrinsic functions use fractional arithmetic with implied fractional values. An implied fractional value is a symbol declared as an integer type, but calculated as a fractional type. Data in a memory location or register can be interpreted as fractional or integer, depending on program needs.

All intrinsic functions that generate multiply or divide instructions perform fractional arithmetic on implied fractional values. (These intrinsic functions are DIV, MPY, MAC, MPYR, and MACR) The relationship between a 16-bit integer and a fractional value is:

Fractional Value = Integer Value / (215)

The relationship between a 32-bit integer and a fractional value is similar:

Fractional Value = Long Integer Value / (231)

The following table shows how 16- and 32-bit values can be interpreted as either fractional or integer values.

Table 1. Interpretation of 16- and 32-bit Values
Type	Hex	Integer Value	Fixed-Point Value
short int	0x2000	8192	0.25
short int	0xE000	-8192	-0.25
long int	0x20000000	536870912	0.25
long int	0xE0000000	-536870912	-0.25

Note: Intrinsic functions use these two macros, Word16. - A macro for signed short, and Word32. - A macro for signed long.