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RE: Connecting IO to the devel boards


What performance do you need? If you need high
performance it would be better to connect the FPGA
to extern DMA and have a simple decoder in the FPGA.

It is simple to get 16 IO pins using the data bits on the 
parallel ports. 16 additional bits is available on port
A and B (if not used is some other way). Then there are
some pins that can be used if the interface is not used
(such as the pins for serial port 2 and 3). If some of
your pins can be dedicated as input or output you can 
find ever more available pins. In most applications
you can get 40-50 IO pins from Etrax to an external

Best Regards

-----Original Message-----
From: owner-dev-etrax@xxxxxxx.com]On">mailto:owner-dev-etrax@xxxxxxx.com]On
Behalf Of Bart Duchesne
Sent: Wednesday, March 07, 2001 1:58 PM
To: dev-etrax
Subject: Connecting IO to the devel boards

Hi guys,

I have the ETRAX development board her before me and I want to connect
alot of IO to it.

I only need digital IO on a TTL level (between 48 and 96 bits or more). 
(the final output drivers are allready present on other boards)

Ideally I would like to build this system around a single FPGA : one
FPGA chip to the parallel ports of the etrax and a lot of IO with little
routing. (I have no FPGA experience at this moment, are there FPGA's
that are in PLCC package so that routing and experimenting with them is
easy ? Tools ? )

Another alternative is to use a couple of 8255 and connect them with a
little bit of glue logic to the etrax parallel ports (complexer design
for routing)

Does anyone have any other ideas or comment ?



Bart Duchesne
Dynamic Data Consulting BVBA
Gijmelbergstraat 19
B - 3201 Landorp

Tel + 32 16 57 25 79
Fax + 32 16 57 25 81