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RE: Memory and wiring



Hi David,

1. You should rely on the library functions for alloction/deallocation
   of memory. Applications with their own memory handlers tend to 
   allocate a huge chunk of memory to be "safe". The Etrax 100 has
   no MMU and this means that this must be allocated in "real" memory.
   A few application unnecessary large memory request may exhaust
   the memory.

2. On our web there is example software for a LCD connected to a
   parallel port. 

http://www.developer.axis.com/download/devboard/devicedriversfordevboard.html

   There are three ways to control the parallel port:

    automatic - Etrax handles handshaking. Used to connect printers.
    manual - Software has control of the handshaking signals. This
             is used by the LCD driver.
    general IO - Software has full control of all pins on the 
                 parallel port. 

    To protect Etrax you can add a buffer (e.g. 74245) on the signals
    you use.

3. JFFS has a garbage collector that also performs some 
   defragmentation when it runs.

Regards,
/Mikael Starvik

-----Original Message-----
From: owner-dev-etrax@xxxxxxx.com]On">mailto:owner-dev-etrax@xxxxxxx.com]On
Behalf Of David Pettersson
Sent: Sunday, September 24, 2000 10:09 AM
To: dev-etrax
Subject: Memory and wiring


Hi,

After having played about with the labcard, I feel I ready to do some
serious stuff with it. First of all, I'd like to know what you suggest
when it comes to memory management; Should I rely on the library functions
for allocating/deallocating memory, or should I simply request a chunk
of memory and use an internal memory manager in the application?

Secondly, is there any suggested way to wire stuff to the card, using
the lp pins? I don't want to risk frying any part of the card, so
I was wondering if you had some recommended way of wiring things to these
pins, or maybe even a schematic?

And finally, when reading/writing to the flash memory, how does the
driver handle fragmenting? Will it become heavily fragmented after
a while, and will it be defragmented at any time?

I'd appreciate any help I can get regarding the above,

Sincerely,

-- 
David Pettersson                            dave@xxxxxxx.org
                                            http://eeyore.se.linux.org
                                            PGP key available on request.