RE: [ECOS] SSI bytes

["Trenton D. Adams" <tadams at theone dot dnsalias dot com>]

Yep, it seems to me that SSI2 would definitely not make a good "SERIAL"
interface driver like that of an RS232 interface.  It's a little odd.
It REQUIRES two bytes at a time to be sent, but you can receive one OR
two bytes at a time.  Since this an extremely odd situation, it would
probably require creating a new standalone driver of some sort that's
not interfaced into any of the existing APIs.  It would think that it
would be silly to interface it with cyg_io_xxx () calls because of these
oddities!?!?


So, I'm going to access the device directly as I need it.

-----Original Message-----
From: ecos-discuss-owner@sources.redhat.com
[mailto:ecos-discuss-owner@sources.redhat.com] On Behalf Of Trenton D.
Adams
Sent: Thursday, September 13, 2001 5:02 PM
To: 'eCos Discussion'
Subject: [ECOS] SSI bytes


The SSI2 interface requires two bytes at a time to be written to the out
FIFO.  The actual communication channel sends one byte at a time, but
requires two to be written to the fifo since the FIFO is 16 bits wide.
Should I make this a block device instead of a standard serial device?

Alternatively, I could add a config option that allows the person to
select whether they want to send two bytes at a time, or just one.  If
two, I'll just write say 0x00ff to the outgoing FIFO if the byte sent
was 0xff.  This could then be configured using the set_config ()
function.  This would however cause half the bandwidth for byte writes
to be wasted.

I was also thinking of just buffering until 2 bytes are received, and
then send both to the FIFO.  If I do this however, then it would be up
to the programmer to write an extra byte if all they wanted to send was
1.  This would also waste half the bandwidth and would cause the
programmer to have to handle this manually.

For the purposes of eCos, what do you guys think would be the best
solution?



Trenton D. Adams
Extreme Engineering
#17, 6025 - 12 St. SE
Calgary, Alberta, Canada
T2H 2K1

Phone: 403 640 9494 ext-208
Fax: 403 640 9599

http://www.extremeeng.com