Freescale Semiconductor SC140 specifications Multi-Precision Arithmetic Support

Models: SC140

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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.

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

 

 

Figure 2-7 shows how the DMAC instruction is implemented.

16-bit Operand 16-bit Operand

>> 16

Multiply

Register Shifter

+

 

 

40-bit Accumulate

Figure 2-7. DMAC Implementation

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SC140 DSP Core Reference Manual

Page 58
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Freescale Semiconductor SC140 specifications Multi-Precision Arithmetic Support, Fractional Multi-Precision Arithmetic