Ieee-to-tms320c3x floating-point format conversion – Texas Instruments TMS320C3x User Manual
Page 122
Floating-Point Conversion (IEEE Std. 754)
5-17
Data Formats and Floating-Point Operation
5.4.1.1
IEEE-to-TMS320C3x Floating-Point Format Conversion
Example 5–4 shows the fast conversion from IEEE to ’C3x floating-point format.
It properly handles the general case when 0 <
e < 255, and also handles 0s (that
is,
e = 0 and f = 0). The other special cases (denormalized, infinity, and NaN)
are not treated and, if present, will give erroneous results.
The fast version of the IEEE-to ’C3x conversion routine was originally developed
by Keith Henry of Apollo Computer, Inc. The other routines were based on this
initial input.
Example 5–4. IEEE-to-TMS320C3x Conversion (Fast Version)
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TITLE IEEE TO TMS320C3x CONVERSION (FAST VERSION)
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SUBROUTINE FMIEEE
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FUNCTION: CONVERSION BETWEEN THE IEEE FORMAT AND THE
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TMS320C3x FLOATING-POINT FORMAT. THE NUMBER TO
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BE CONVERTED IS IN THE LOWER 32 BITS OF R0.
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THE RESULT IS STORED IN THE UPPER 32 BITS OF R0.
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UPON ENTERING THE ROUTINE, AR1 POINTS TO THE
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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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ARGUMENT
ASSIGNMENTS:
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ARGUMENT
|
FUNCTION
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–––––––––––+–––––––––––––––––––––––––––––––––––––
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R0
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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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