FYI-only:
---------

I'm eagerly awaiting the arrival of the PIC18F4620 as the "big brother" to
my favorite PIC18F452 PICmicro. Besides having twice the program memory as
the PIC18F452, the PIC18F4620 has a lot going for it and will only cost
around $1.22 more than the PIC18F452 (in single quantity, source is Mouser).
I've just started skimming this new data sheet, and it's like having a
PIC18F452 on steroids! One notable thing I noticed is an extension to the
PIC18 instruction set with 8 new instructions. This does not come without
caveats (as noted in the data sheet), so if anyone is interested in these
new instructions, check out the recently released PIC18F2525/2620/4525/4620
data sheet. I'm pretty sure other new PIC18F PICmicros will also include
these extensions to the instruction set, but I'm just focusing on the
PIC18F4620 in this post because of it's migration upgrade path potential
from the PIC18F452.


From the data sheet:
--------------------
{
The extended instructions are specifically implemented
to optimize re-entrant program code (that is, code that
is recursive or that uses a software stack) written in
high-level languages, particularly C. Among other
things, they allow users working in high-level
languages to perform certain operations on data
structures more efficiently. These include:

  dynamic allocation and de-allocation of software stack
  space when entering and leaving subroutines
  function pointer invocation
  software stack pointer manipulation
  manipulation of variables located in a software


The instruction set extension and the
Indexed Literal Offset Addressing mode
were designed for optimizing applications
written in C; the user may likely never use
these instructions directly in assembler.
The syntax for these commands is provided
as a reference for users who may be
reviewing code that has been generated
by a compiler.
}



Best regards,

Ken Pergola

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