Datasheet

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

architecture, 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 several options selected through

various bits in the CPU Core Configuration register

(CORCON), which are:

1. Fractional or integer DSP multiply (IF).

2. Signed or unsigned DSP multiply (US).

3. Conventional or convergent rounding (RND).

4. Automatic saturation on/off for ACCA (SATA).

5. Automatic saturation on/off for ACCB (SATB).

6. Automatic saturation on/off for writes to data

memory (SATDW).

7. Accumulator Saturation mode selection

(ACCSAT).

A block diagram of the DSP engine is shown in

Figure 2-2.

TABLE 2-2: DSP INSTRUCTION

SUMMARY

Instruction

Algebraic

Operation

ACC WB?

CLR A = 0 Yes

ED A = (x – y)

EDAC A = A + (x – y)

MAC A = A + (x * y) Yes

MAC A = A + x

MOVSAC No change in A Yes

MPY A = x • y No

MPY.N A = – x • y No

MSC A = A – x • y Yes

Note: For CORCON layout, see Table 3-3.