Texas Instruments TMS320C3x User Manual
Page 125
Floating-Point Conversion (IEEE Std. 754)
5-20
Example 5–5.IEEE-to-TMS320C3x Conversion (Complete Version) (Continued)
*
HANDLE NaN AND INFINITY
TSTB
*+AR1(7),R0
RETSNZ
;
Return if NaN
LDI
R0,R0
LDFGT
*+AR1(8),R0
;
If positive, infinity =
;
most positive number
LDFN
*+AR1(5),R0
;
If negative, infinity =
RETS
;
most negative number RETS
*
HANDLE 0s AND UNNORMALIZED NUMBERS
UNNORM
TSTB
*+AR1(6),R0
;
Is the MSB of f equal to 1?
LDFZ
*+AR1(3),R0
;
If not, force the number to 0
RETSZ
;
and return
XOR
*+AR1(6),R0
;
If MSB of f = 1, make it 0
BND
NEG1
LSH
1,R0
;
Eliminate sign bit
;
& line up mantissa
SUBI
*+AR1(2),R0
;
Make e =
±
127
PUSH
R0
POPF
R0
;
Put number in floating point format
RETS
NEG1
POPF
R0
NEGF
R0,R0
;
If negative, negate R0
RETS
*
HANDLE THE REGULAR CASES
*
NORMAL
AND3
R0,*AR1,R1
;
Replace fraction with 0
BND
NEG
;
Test sign
ADDI
R0,R1
;
Shift sign and exponent inserting 0
SUBI
*+AR1(2),R1
;
Unbias exponent
PUSH
R1
POPF
R0
;
Load this as a flt. pt. number
RETS
NEG
POPF
R0
;
Load this as a flt. pt. number
NEGF
R0,R0
;
Negate if original sign negative
RETS