© 2006 Microchip Technology Inc. DS70117F-page 15
dsPIC30F6011/6012/6013/6014
2.0 CPU ARCHITECTURE
OVERVIEW
2.1 Core Overview
This section contains a brief overview of the CPU
architecture of the dsPIC30F. For additional hard-
ware and programming information, please refer to
the “dsPIC30F Family Reference Manual” (DS70046)
and the “dsPIC30F/33F Programmer’s Reference
Manual” (DS70157) respectively.
The core has a 24-bit instruction word. The Program
Counter (PC) is 23 bits wide with the Least Significant
bit (LSb) always clear (refer to Section 3.1 “Program
Address Space”), and the Most Significant bit (MSb)
is ignored during normal program execution, except for
certain specialized instructions. Thus, the PC can
address up to 4M instruction words of user program
space. An instruction prefetch mechanism is used to
help maintain throughput. Program loop constructs,
free from loop count management overhead, are sup-
ported using the DO and REPEAT instructions, both of
which are interruptible at any point.
The working register array consists of 16 x 16-bit regis-
ters, each of which can act as data, address or offset
registers. One working register (W15) operates as a
software Stack Pointer for interrupts and calls.
The data space is 64 Kbytes (32K words) and is split
into two blocks, referred to as X and Y data memory.
Each block has its own independent Address Genera-
tion Unit (AGU). Most instructions operate solely
through the X memory, AGU, which provides the
appearance of a single unified data space. The
Multiply-Accumulate (MAC) class of dual source DSP
instructions operate through both the X and Y AGUs,
splitting the data address space into two parts (see
Section 3.2 “Data Address Space”). The X and Y
data space boundary is device specific and cannot be
altered by the user. Each data word consists of 2 bytes,
and most instructions can address data either as words
or bytes.
There are two methods of accessing data stored in
program memory:
• The upper 32 Kbytes of data space memory can
be mapped into the lower half (user space) of pro-
gram space at any 16K program word boundary,
defined by the 8-bit Program Space Visibility Page
(PSVPAG) register. This lets any instruction
access program space as if it were data space,
with a limitation that the access requires an addi-
tional cycle. Moreover, only the lower 16 bits of
each instruction word can be accessed using this
method.
• Linear indirect access of 32K word pages within
program space is also possible using any working
register, via table read and write instructions.
Table read and write instructions can be used to
access all 24 bits of an instruction word.
Overhead-free circular buffers (Modulo Addressing)
are supported in both X and Y address spaces. This is
primarily intended to remove the loop overhead for
DSP algorithms.
The X AGU also supports Bit-Reversed Addressing on
destination effective addresses to greatly simplify input
or output data reordering for radix-2 FFT algorithms.
Refer to Section 4.0 “Address Generator Units” for
details on Modulo and Bit-Reversed Addressing.
The core supports Inherent (no operand), Relative,
Literal, Memory Direct, Register Direct, Register
Indirect, Register Offset and Literal Offset Addressing
modes. Instructions are associated with predefined
addressing modes, depending upon their functional
requirements.
For most instructions, the core is capable of executing
a data (or program data) memory read, a working reg-
ister (data) read, a data memory write and a program
(instruction) memory read per instruction cycle. As a
result, 3-operand instructions are supported, allowing
C = A + B operations to be executed in a single cycle.
A DSP engine has been included to significantly
enhance the core arithmetic capability and throughput.
It features a high-speed 17-bit by 17-bit multiplier, a
40-bit ALU, two 40-bit saturating accumulators and a
40-bit bidirectional barrel shifter. Data in the accumula-
tor or any working register can be shifted up to 15 bits
right, or 16 bits left in a single cycle. The DSP instruc-
tions operate seamlessly with all other instructions and
have been designed for optimal real-time performance.
The MAC class of instructions can concurrently fetch
two data operands from memory while multiplying two
W registers. To enable this concurrent fetching of data
operands, the data space has been split for these
instructions and linear for all others. This has been
achieved in a transparent and flexible manner, by ded-
icating certain working registers to each address space
for the MAC class of instructions.
Note: This data sheet summarizes features of this group
of dsPIC30F devices and is not intended to be a complete
reference source. For more information on the CPU,
peripherals, register descriptions and general device
functionality, refer to the “dsPIC30F Family Reference
Manual” (DS70046). For more information on the device
instruction set and programming, refer to the “dsPIC30F/
33F Programmer’s Reference Manual” (DS70157).
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