2-22
SC140 DSP Core Reference Manual
DALU
Figure 2-5 shows the four cases for rounding a number in the Dn.h register. If scaling is set in the SR, the
rounding position is updated to reflect the alignment of the result when it is put on the data bus. However,
the contents of the register are not scaled.
Figure 2-5. Convergent Rounding (No Scaling)
Case I
: If D0.l < $8000 (1/2), then round down (add nothing)
Before Rounding
After Rounding
Case II
: If D0.l > $8000 (1/2), then round up (add 1 to D0.h)
Case III
: If D0.l = $8000 (1/2), and the LSB of D0.h= 0, then round down (add nothing)
Case IV
: If D0.l = $8000 (1/2), and the LSB of Do.h = 1, then round up (add 1 to D0.h)
*D0.l is always clear, performed during RND, MPYR, and MACR.
X X . . X X X X X . . . X X X 0 1 0 0 0 1 1 X X X . . . . X X X
39
32 31
16 15
0
D0.e
D0.h
D0.l
0
X X . . X X X X X . . . X X X 0 1 0 0 0 0 0 . . . . . . . . . 0 0 0
39
32 31
16 15
0
D0.e
D0.h
D0.l*
Before Rounding
After Rounding
X X . . X X X X X . . . X X X 0 1 0 0 1 1 1 0 X X . . . . X X X
39
32 31
16 15
0
D0.e
D0.h
D0.l
1
X X . . X X X X X . . . X X X 0 1 0 1 0 0 0 . . . . . . . . . 0 0 0
39
32 31
16 15
0
D0.e
D0.h
D0.l*
Before Rounding
After Rounding
X X . . X X X X X . . . X X X 0 1 0 0 1 0 0 0 . . . . . . . . 0 0 0
39
32 31
16 15
0
D0.e
D0.h
D0.l
0
X X . . X X X X X . . . X X X 0 1 0 0 0 0 0 . . . . . . . . . 0 0 0
39
32 31
16 15
0
D0.e
D0.h
D0.l*
Before Rounding
After Rounding
X X . . X X X X X . . . X X X 0 1 0 1 1 0 0 0 . . . . . . . . 0 0 0
39
32 31
16 15
0
D0.e
D0.h
D0.l
1
X X . . X X X X X . . . X X X 0 1 1 0 0 0 0 . . . . . . . . . 0 0 0
39
32 31
16 15
0
D0.e
D0.h
D0.l*
Summary of Contents for SC140 DSP Core
Page 12: ...xii SC140 DSP Core Reference Manual ...
Page 18: ...xviii SC140 DSP Core Reference Manual ...
Page 32: ...1 6 SC140 DSP Core Reference Manual Core Architecture Features ...
Page 180: ...4 70 SC140 DSP Core Reference Manual Trace Unit Registers ...
Page 250: ...6 70 SC140 DSP Core Reference Manual Programming Rules ...
Page 314: ...7 64 SC140 DSP Core Reference Manual NOP Definition ...
Page 463: ...DI SC140 DSP Core Reference Manual A 149 15 8 7 0 DI 1 1 4 1 0 0 1 1 1 1 1 0 1 1 1 1 1 0 1 ...
Page 478: ...A 164 SC140 DSP Core Reference Manual EI ...
Page 618: ...A 304 SC140 DSP Core Reference Manual MOVES 4F s15 sssssssssssssss Signed 15 bit offset ...
Page 638: ...A 324 SC140 DSP Core Reference Manual MPYR ...
Page 746: ...A 432 SC140 DSP Core Reference Manual ZXTA x ...
Page 758: ...I 10 Index ...
Page 759: ...SC140 DSP Core Reference Manual i ...
Page 760: ......