Datasheet

 2010 Microchip Technology Inc. DS70138G-page 19
dsPIC30F3014/4013
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 Tabl e 2-2 for DSP instructions.)
The DSP engine has various options selected through
various bits in the CPU Core Configuration register
(CORCON), as listed below:
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.
Note: For CORCON layout, see Table 3-3 .
TABLE 2-2: DSP INSTRUCTION
SUMMARY
Instruction
Algebraic
Operation
ACC WB?
CLR A = 0 Yes
ED A = (x – y)
2
No
EDAC A = A + (x – y)
2
No
MAC A = A + (x * y) Yes
MAC A = A + x2 No
MOVSAC No change in A Yes
MPY A = x * y No
MPY.N A = – x * y No
MSC A = A – x * y Yes