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Message
From: "Jerrold Wen" <jwen@v...>
Date: Tue, 26 Aug 2003 11:06:23 -0400
Subject: RE: [oc] 12bit data in 16bit packets?
Hi Jim,
You are correct. I am packaging data for transport over hi-speed USB.
However, I am using an off-the-shelf serializer so I have no control over
that section - though your idea would be great if I did. I am writing to a
16bit wide FIFO memory. The data bus in my design is 12 bits, and I just
fill the 4 high bits with zeroes.
Jerrold.
-----Original Message-----
From: owner-cores@o... [mailto:owner-cores@o...] On Behalf
Of Jim Dempsey
Sent: August 25, 2003 2:24 PM
To: cores@o...
Subject: Re: [oc] 12bit data in 16bit packets?
I will assume because you are using "bandwidth" and "sending zeros" that you
must be referring to a serial transmission system and not memory storage.
Most serial transmission systems consist of a Latch/Shift Register setup.
i.e. Parallel In - Serial Out. If you are sending data synchronously then
you can modify the shift counter (e.g. 4 bit up counter) to pre-load with 4
in addition to 0. In this manner the parallel in clocks every 12 shifts. A
standard 16-bit shift register can be used for both 12-bit and 16-bit
transmissions.
It might help if you can elaborate on transmission requirements and
restrictions.
Jim
----- Original Message -----
From: "Jerrold Wen" <jwen@v...>
To: <cores@o...>
Sent: Monday, August 25, 2003 9:57 AM
Subject: [oc] 12bit data in 16bit packets?
Hi all,
Does anyone have any good ideas on how to pack 12bit data in to 16bit
packets so that the extra bandwith is not wasted sending zeroes? I was
thinking of using something like a four word FIFO and a barrel shifter. For
every four 12-bit words that are input, three 16bit words are output. One
clock is used up at the beginning to 'arm' the FIFO.
Are there any other techniques for this?
Thanks,
Jerrold.
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