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Re: FastFlashDisks (esp. data integrity)

From: "Brian Empey, P.Eng." <>
Date: Tue, 22 Jul 2003 09:35:23 -0700

RE Data Integrity:

If FireWire is like USB, then you're both correct.
Here's why:

In USB there are 3 modes of operation (going by memory from my first USB
design in 1998)
- bulk (as in hard-drives, etc.)
- control (accessing the settings on the USB device, such as configuring
a joy-stick, etc)
- isochronous (real-time data ... for digital speakers in USB 1.x,
cameras also in USB 2.0)

In BULK MODE the data integrity is most important and there are checks
and retransmissions.
In ISOCHRONOUS MODE the timing is most important so there are no checks
and retransmissions.

If your FireWire camera is being used as a camera, then it must send
data in real-time and cannot retransmit.
But if its used as a data storage device, then it will retry until it
gets the correct data.

The designers of both USB and FIREWIRE are smart engineers and they have
all the bases covered!

Brian

PS: You don't really need a PC for USB either.  Our 2" square computer
modules have USB host ports and talk to all devices from DiskOnKey to
digital cameras to 802.11b WiFi dongles.

Bryan Hurley wrote:
> 
> no prob about the name..  

> 1)I swear I hooked up a sony camera to a desktop and transferred video
> using
> some video editing software.. this dropped some frames.. but it seems like
> the software was decoding and then capturing the images as they came
> instead of transferring a data file...
> 
> Bryan Hurley
> 
> On Mon, 21 Jul 2003, Carol Stein wrote:
> 
> > Hi, Brian --
> >
> > So does this mean that the protocol for the "Firewire" interface now *does*
> > include error checking? I must have missed that update in my scanning of
> > techie materials. No argument intended (unlike in my political posts in
> > other forums!); just trying to get accurate information.
> >
> > Cheers --
> > Carol
>

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