Texas Instruments TMS320C3x User Manual
Page 124
Floating-Point Conversion (IEEE Std. 754)
5-19
Data Formats and Floating-Point Operation
Example 5–5. IEEE-to-TMS320C3x Conversion (Complete Version)
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TITLE IEEE TO TMS320C3x CONVERSION (COMPLETE VERSION)
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*
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SUBROUTINE FMIEEE1
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FUNCTION: CONVERSION BETWEEN THE IEEE FORMAT AND THE TMS320C3x
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FLOATING-POINT FORMAT. THE NUMBER TO BE CONVERTED
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IS IN THE LOWER 32 BITS OF R0. THE RESULT IS STORED
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IN THE UPPER 32 BITS OF R0.
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*
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UPON ENTERING THE ROUTINE, AR1 POINTS TO THE FOLLOWING TABLE:
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*
(0) 0xFF800000 <
– –
AR1
*
(1) 0xFF000000
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(2) 0x7F000000
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(3) 0x80000000
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(4) 0x81000000
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(5) 0x7F800000
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(6) 0x00400000
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(7) 0x007FFFFF
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(8) 0x7F7FFFFF
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ARGUMENT
ASSIGNMENTS:
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ARGUMENT
|
FUNCTION
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–––––––––––+–––––––––––––––––––––––––––––––––––––
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R0
|
NUMBER TO BE CONVERTED
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AR1
|
POINTER TO TABLE WITH CONSTANTS
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REGISTERS USED AS INPUT: R0, AR1
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REGISTERS MODIFIED: R0, R1
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REGISTER CONTAINING RESULT: R0
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NOTE:
SINCE THE STACK POINTER SP IS USED, MAKE SURE TO
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INITIALIZE IT IN THE CALLING PROGRAM.
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CYCLES: 23 (WORST CASE) WORDS: 34
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.global
FMIEEE1
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FMIEEE1
LDI
R0,R1
AND
*+AR1(5),R1
BZ
UNNORM
;
If e = 0, number is either 0 or
*
;
denormalized
XOR
*+AR1(5),R1
BNZ
NORMAL
;
If e < 255, use regular routine