PIC24FJ64GA705 Datasheet, PDF (35/412 Pages) –

PIC24FJ256GA705 FAMILY
3.0 CPU
Note:
This data sheet summarizes the features of
this group of PIC24F devices. It is not
intended to be a comprehensive reference
source. For more information on the CPU,
refer to the “dsPIC33/PIC24 Family Ref-
erence Manual”, “CPU with Extended
Data Space (EDS)” (DS39732), which is
available from the Microchip web site
(www.microchip.com). The information in
this data sheet supersedes the
information in the FRM.
The PIC24F CPU has a 16-bit (data) modified Harvard
architecture with an enhanced instruction set and a
24-bit instruction word with a variable length opcode
field. The Program Counter (PC) is 23 bits wide and
addresses up to 4M instructions of user program
memory space. A single-cycle instruction prefetch
mechanism is used to help maintain throughput and
provides predictable execution. All instructions execute
in a single cycle, with the exception of instructions that
change the program flow, the double-word move
(MOV.D) instruction and the table instructions.
Overhead-free program loop constructs are supported
using the REPEAT instructions, which are interruptible
at any point.
PIC24F devices have sixteen, 16-bit Working registers
in the programmer’s model. Each of the Working
registers can act as a Data, Address or Address Offset
register. The 16^th Working register (W15) operates as
a Software Stack Pointer (SSP) for interrupts and calls.
The lower 32 Kbytes of the Data Space (DS) can be
accessed linearly. The upper 32 Kbytes of the Data
Space are referred to as Extended Data Space (EDS),
to which the extended data RAM, EPMP memory
space or program memory can be mapped.
The Instruction Set Architecture (ISA) has been
significantly enhanced beyond that of the PIC18, but
maintains an acceptable level of backward compatibil-
ity. All PIC18 instructions and addressing modes are
supported, either directly, or through simple macros.
Many of the ISA enhancements have been driven by
compiler efficiency needs.
The core supports Inherent (no operand), Relative,
Literal, Memory Direct Addressing modes along with
three groups of addressing modes. All modes support
Register Direct and various Register Indirect modes.
Each group offers up to seven 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, three parameter instructions can be supported,
allowing trinary operations (that is, A + B = C) to be
executed in a single cycle.
A high-speed, 17-bit x 17-bit multiplier has been included
to significantly enhance the core arithmetic capability and
throughput. The multiplier supports Signed, Unsigned
and Mixed mode, 16-bit x 16-bit or 8-bit x 8-bit, integer
multiplication. All multiply instructions execute in a single
cycle.
The 16-bit ALU has been enhanced with integer divide
assist hardware that supports an iterative non-restoring
divide algorithm. It operates in conjunction with the
REPEAT instruction looping mechanism and a selection
of iterative divide instructions to support 32-bit (or 16-bit),
divided by 16-bit, integer signed and unsigned division.
All divide operations require 19 cycles to complete but
are interruptible at any cycle boundary.
The PIC24F has a vectored exception scheme with up
to 8 sources of non-maskable traps and up to 118 inter-
rupt sources. Each interrupt source can be assigned to
one of seven priority levels.
A block diagram of the CPU is shown in Figure 3-1.
3.1 Programmer’s Model
The programmer’s model for the PIC24F is shown in
Figure 3-2. All registers in the programmer’s model are
memory-mapped and can be manipulated directly by
instructions.
A description of each register is provided in Table 3-1.
All registers associated with the programmer’s model
are memory-mapped.
 2016 Microchip Technology Inc.
DS30010118B-page 35