Freescale Semiconductor StarCore SC140 - Manual (Page 58)

2-26 SC140 DSP Core Reference Manual
DALU
2.2.2.8 Multi-Precision Arithmetic Support
The SC140 DALU supports multi-precision arithmetic for fractional and integer operations.
2.2.2.8.1 Fractional Multi-Precision Arithmetic
A set of DALU instructions is provided for fractional multi-precision multiplications. When these
instructions are used, the multiplier accepts some combinations of two’s complement signed and unsigned
formats. Table 2-15 lists these instructions.
Figure 2-7 shows how the DMAC instruction is implemented.
Figure 2-7. DMAC Implementation
Table 2-15. Fractional Signed and Unsigned Two’s Complement Multiplication
Instruction Description
MPYSU/MACSU Fractional multiplication and multiply-accumulate with signed
× unsigned operands
MPYUS/MACUS Fractional multiplication and multiply-accumulate with unsigned
× signed operands
MPYUU/MACUU Fractional multiplication and multiply-accumulate with unsigned
× unsigned operands
DMACSS Fractional multiplication with signed
× signed operands and 16-bit arithmetic right shift
of the accumulator before accumulation
DMACSU Fractional multiplication with signed
× unsigned operands and 16-bit arithmetic right
shift of the accumulator before accumulation
Multiply
+
40-bit Accumulate
Register Shifter
>> 16
16-bit Operand 16-bit Operand