DSPIC33FJ64GP706 datasheet(64/322 Pages) MICROCHIP

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dsPIC33FJXXXGPX06/X08/X10

DS70286C-page 62

TABLE 4-35:

FUNDAMENTAL ADDRESSING MODES SUPPORTED

4.3.3

MOVE AND ACCUMULATOR

INSTRUCTIONS

Move instructions and the DSP accumulator class of

instructions provide a greater degree of addressing

flexibility than other instructions. In addition to the

Addressing

modes

supported

most

MCU

instructions, move and accumulator instructions also

support Register Indirect with Register Offset

Addressing mode, also referred to as Register Indexed

mode.

In summary, the following Addressing modes are

supported by move and accumulator instructions:

• Register Direct

• Register Indirect

• Register Indirect Post-modified

• Register Indirect Pre-modified

• Register Indirect with Register Offset (Indexed)

• Register Indirect with Literal Offset

• 8-bit Literal

• 16-bit Literal

4.3.4

MAC

INSTRUCTIONS

The dual source operand DSP instructions (CLR, ED,

EDAC

, MAC, MPY, MPY.N, MOVSAC and MSC), also referred

to as MAC instructions, utilize a simplified set of

addressing modes to allow the user to effectively

manipulate the data pointers through register indirect

tables.

The 2-source operand prefetch registers must be

members of the set {W8, W9, W10, W11}. For data

reads, W8 and W9 are always directed to the X RAGU

and W10 and W11 will always be directed to the Y

AGU. The effective addresses generated (before and

after modification) must, therefore, be valid addresses

within X data space for W8 and W9 and Y data space

for W10 and W11.

In summary, the following addressing modes are

supported by the MAC class of instructions:

• Register Indirect

• Register Indirect Post-Modified by 2

• Register Indirect Post-Modified by 4

• Register Indirect Post-Modified by 6

• Register Indirect with Register Offset (Indexed)

4.3.5

OTHER INSTRUCTIONS

Besides the various addressing modes outlined above,

some instructions use literal constants of various sizes.

For example, BRA (branch) instructions use 16-bit signed

literals to specify the branch destination directly, whereas

the DISI instruction uses a 14-bit unsigned literal field. In

some instructions, such as ADD Acc, the source of an

operand or result is implied by the opcode itself. Certain

operations, such as NOP, do not have any operands.

4.4

Modulo Addressing

Modulo Addressing mode is a method of providing an

automated means to support circular data buffers using

hardware. The objective is to remove the need for

software to perform data address boundary checks

when executing tightly looped code, as is typical in

many DSP algorithms.

Modulo Addressing can operate in either data or program

space (since the data pointer mechanism is essentially

the same for both). One circular buffer can be supported

in each of the X (which also provides the pointers into

program space) and Y data spaces. Modulo Addressing

Addressing Mode

Description

File Register Direct

The address of the file register is specified explicitly.

The contents of a register are accessed directly.

The contents of Wn forms the EA.

The contents of Wn forms the EA. Wn is post-modified (incremented or

decremented) by a constant value.

Wn is pre-modified (incremented or decremented) by a signed constant value

to form the EA.

The sum of Wn and a literal forms the EA.

Note:

For the MOV instructions, the Addressing

mode specified in the instruction can differ

for the source and destination EA.

However, the 4-bit Wb (Register Offset)

field is shared between both source and

destination (but typically only used by

one).

Note:

Not all instructions support all the

Addressing modes given above. Individual

instructions may support different subsets

of these Addressing modes.

Note:

Addressing mode is only available for W9

(in X space) and W11 (in Y space).

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