Texas Instruments TMS320C3x 사용자 설명서

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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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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UPON ENTERING THE ROUTINE, AR1 POINTS TO THE FOLLOWING TABLE:

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(0) 0xFF800000 <

– –

 AR1

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(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

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FUNCTION

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–––––––––––+–––––––––––––––––––––––––––––––––––––

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R0

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NUMBER TO BE CONVERTED

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AR1

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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

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If e = 0, number is either 0 or

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denormalized

XOR

*+AR1(5),R1

BNZ

NORMAL

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If e < 255, use regular routine