gnupic: Help/Hint needed
Subject:
Re: Help/Hint needed
From:
Wojciech Zabolotny ####@####.####
Date:
19 Jan 2001 00:05:49 -0000
Message-Id: <20010118230652.A1476@wzab.nasz.dom>
On Thu, Jan 18, 2001 at 09:56:03AM -0700, James H . grosbach wrote:
> > I wonder if someone out there knows the answers (or some hints) to the
> > following questions about the PIC16F and PIC18C families.
> >
> > 1) Can I have an external ROM or Flash (say 512K or more)holding some
> > instructions and then read them from PIC in real-time. (the problem is that
> > PIC program memory may not be enough to hold the entire program.)
>
> Not currently. The 18C family is designed with this in mind, but no 16 or 18
> parts are currently available with an external address bus.
>
However it is possible to put the self-written interpreter into the PIC's
internal code memory, connect the external memory using the ports
(it can be done with single 8-bit port, eg. PORTD in 16F877 and two latches,
one for lower byte of address and the another for higher byte <certainly
there are a few control lines required as well - eg. LOW_ADD_STB,
HIGH_ADD_STB, MEM_RD and for RAM: MEM_WR - total 12 lines>),
and put the "bytecode" for that interpreter into the external EPROM.
Such solution may be quite efficient for bigger projects, when often used
procedures are coded in assembly, optimized and located in the internal code
memory, while the external bytecode is responsible only for "higher level"
structure of the program.
--
Regards
Wojciech Zabolotny
####@####.####
