Texas Instruments TMS320C64X - Manual (Page 152)

Fractional Q Formats
A-4
A.2.3 Q.31 Format
Q.31 format spans two 16-bit memory words. The 16-bit word stored in the
lower memory location contains the 16 least significant bits, and the higher
memory location contains the most significant 15 bits and the sign bit. The
approximate allowable range of numbers in Q.31 representation is (−1,1) and
the finest fractional resolution is 2
−31 = 4.66 × 10 −10 .
Table A−3. Q.31 Low Memory Location Bit Fields
Bit 15 14 13 12
…
3 2 1 0
Value Q15 Q14 Q13 Q12 … Q3 Q2 Q1 Q0
Table A−4. Q.31 High Memory Location Bit Fields
Bit 15 14 13 12 … 3 2 1 0
Value S Q30 Q29 Q28 … Q19 Q18 Q17 Q16