Motorola DSP96002 - Manual (Page 765)

MOTOROLA DSP96002 USER’S MANUAL D-13
ure D-10b. Note that the 52-bit fraction may actually consist of zeros (21 or 29) if the number in question
was the result of a SEP arithmetic or a SP move. SEP arithmetic result precision can only be retained in
memory by using DP moves.
D.1.5.1.1 FLOATING-POINT MOVES TO/FROM DATA ALU REGISTERS
The following sections deal with the case where a write (move in) is followed by a read (move out) without
any floating-point operation being actually performed on the Data ALU register (save-restore procedure).
The only way to provide correct results for save-restore procedures is to perform the same type of moves
when writing and then reading the register (SP write followed by SP read or DP write followed by DP read).
D.1.5.1.1.1 Single Precision (SP) Move Of A SP Normalized Number
This section describes what happens when a 32-bit source (normalized single precision) is writen by a sin-
gle precision floating-point move and the data is stored in a Data ALU floating-point register D0-D9. Fol-
lowing the above operation, the Data ALU register will be read first by a single precision and then by a dou-
ble precision floating-point move.
- 32-bit data from source is 3F800000 (= +1.0)
- exp = 7F (8 bit bias)
- mantissa = 000000 (the hidden bit is one)
- data stored in the register
- e = 3FF (correct representation with 11-bit bias)
- I = 1 (the number is normalized so hidden bit is 1)
- U-TAG = 0 (cleared; the number can be used in computations
without adding extra cycles for normalization,
since it is a normalized number) - fraction
= 00...00 - mantissa = 1.00...00