DSPIC30F3012AT20ESLASHML datasheet(23/205 Pages) MICROCHIP

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DS70139E-page 21

dsPIC30F2011/2012/3012/3013

2.4

DSP Engine

The DSP engine consists of a high-speed 17-bit x

17-bit multiplier, a barrel shifter and a 40-bit adder/

subtracter (with two target accumulators, round and

saturation logic).

The DSP engine also has the capability to perform

inherent

accumulator-to-accumulator

operations,

which require no additional data. These instructions are

ADD, SUB

and NEG.

The dsPIC30F is a single-cycle instruction flow archi-

tecture, therefore, concurrent operation of the DSP

engine with MCU instruction flow is not possible.

However, some MCU ALU and DSP engine resources

may be used concurrently by the same instruction (e.g.,

ED, EDAC

). See Table 2-2.

The DSP engine has various options selected through

various bits in the CPU Core Configuration register

(CORCON), as listed below:

Fractional or integer DSP multiply (IF).

Signed or unsigned DSP multiply (US).

Conventional or convergent rounding (RND).

Automatic saturation on/off for ACCA (SATA).

Automatic saturation on/off for ACCB (SATB).

Automatic saturation on/off for writes to data

memory (SATDW).

Accumulator

Saturation

mode

selection

(ACCSAT).

A block diagram of the DSP engine is shown in

Figure 2-2.

Note:

For CORCON layout, see Table 3-3.

TABLE 2-2:

DSP INSTRUCTION SUMMARY

Instruction

Algebraic Operation

ACC WB?

CLR

A = 0

Yes

A = (x – y)2

EDAC

A = A + (x – y)2

MAC

A = A + (x * y)

Yes

MAC

A = A + x2

MOVSAC

No change in A

Yes

MPY

A = x * y

MPY.N

A = – x * y

MSC

A = A – x * y

Yes

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